spell 'acked' consistently

Only use upper-case "ACK" to refer to the frames.
diff --git a/src/lib.rs b/src/lib.rs
index b1fb7ed..b4da027 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -578,7 +578,7 @@
     /// A bidirectional stream is considered completed when all incoming data
     /// has been read by the application (up to the `fin` offset) or the
     /// stream's read direction has been shutdown, and all outgoing data has
-    /// been ACKed by the peer (up to the `fin` offset) or the stream's write
+    /// been acked by the peer (up to the `fin` offset) or the stream's write
     /// direction has been shutdown.
     ///
     /// The default value is `0`.
@@ -736,7 +736,7 @@
     /// Whether the connection handshake has been confirmed.
     handshake_confirmed: bool,
 
-    /// Whether an ACK-eliciting packet has been sent since last receiving a
+    /// Whether an ack-eliciting packet has been sent since last receiving a
     /// packet.
     ack_eliciting_sent: bool,
 
@@ -1383,13 +1383,13 @@
             self.process_frame(frame, epoch, now)?;
         }
 
-        // Process ACK'd frames.
+        // Process acked frames.
         for acked in self.recovery.acked[epoch].drain(..) {
             match acked {
                 frame::Frame::ACK { ranges, .. } => {
                     // Stop acknowledging packets less than or equal to the
                     // largest acknowledged in the sent ACK frame that, in
-                    // turn, got ACK'd.
+                    // turn, got acked.
                     if let Some(largest_acked) = ranges.largest() {
                         self.pkt_num_spaces[epoch]
                             .recv_pkt_need_ack
@@ -1424,7 +1424,7 @@
         }
 
         // We only record the time of arrival of the largest packet number
-        // that still needs to be ACK'd, to be used for ACK delay calculation.
+        // that still needs to be acked, to be used for ACK delay calculation.
         if self.pkt_num_spaces[epoch].recv_pkt_need_ack.largest() < Some(pn) {
             self.pkt_num_spaces[epoch].largest_rx_pkt_time = now;
         }
@@ -1991,7 +1991,7 @@
 
         self.max_send_bytes = self.max_send_bytes.saturating_sub(written);
 
-        // (Re)start the idle timer if we are sending the first ACK-eliciting
+        // (Re)start the idle timer if we are sending the first ack-eliciting
         // packet since last receiving a packet.
         if ack_eliciting &&
             !self.ack_eliciting_sent &&
@@ -2143,7 +2143,7 @@
     /// When the `direction` argument is set to [`Shutdown::Read`], outstanding
     /// data in the stream's receive buffer is dropped, and no additional data
     /// is added to it. Data received after calling this method is still
-    /// validated and ACKed but not stored, and [`stream_recv()`] will not
+    /// validated and acked but not stored, and [`stream_recv()`] will not
     /// return it to the application.
     ///
     /// When the `direction` argument is set to [`Shutdown::Write`], outstanding
@@ -3565,7 +3565,7 @@
         assert!(pipe.server.handshake_completed);
         assert!(!pipe.server.handshake_confirmed);
 
-        // Client ACKs 1-RTT packet.
+        // Client acks 1-RTT packet.
         len = testing::recv_send(&mut pipe.client, &mut buf, len).unwrap();
 
         assert!(pipe.client.handshake_completed);
@@ -3583,12 +3583,12 @@
         assert!(pipe.server.handshake_completed);
         assert!(pipe.server.handshake_confirmed);
 
-        // Client sends 1-RTT ACK-eliciting packet.
+        // Client sends 1-RTT ack-eliciting packet.
         assert_eq!(pipe.client.stream_send(0, b"a", false), Ok(1));
 
         len = testing::recv_send(&mut pipe.client, &mut buf, len).unwrap();
 
-        // Server ACKs 1-RTT packet.
+        // Server acks 1-RTT packet.
         len = testing::recv_send(&mut pipe.server, &mut buf, len).unwrap();
 
         assert!(pipe.client.handshake_completed);
diff --git a/src/recovery.rs b/src/recovery.rs
index d7016fa..45e5222 100644
--- a/src/recovery.rs
+++ b/src/recovery.rs
@@ -195,7 +195,7 @@
     ) -> Result<()> {
         let largest_acked = ranges.largest().unwrap();
 
-        // If the largest packet number ACKed exceeds any packet number we have
+        // If the largest packet number acked exceeds any packet number we have
         // sent, then the ACK is obviously invalid, so there's no need to
         // continue further.
         if largest_acked > self.largest_sent_pkt[epoch] {
@@ -229,7 +229,7 @@
 
         let mut has_newly_acked = false;
 
-        // Processing ACKed packets in reverse order (from largest to smallest)
+        // Processing acked packets in reverse order (from largest to smallest)
         // appears to be faster, possibly due to the BTreeMap implementation.
         for pn in ranges.flatten().rev() {
             let newly_acked = self.on_packet_acked(pn, epoch);
diff --git a/src/stream.rs b/src/stream.rs
index 9299622..d5ec17d 100644
--- a/src/stream.rs
+++ b/src/stream.rs
@@ -412,7 +412,7 @@
     ///
     /// For bidirectional streams this happens when both the receive and send
     /// sides are complete. That is when all incoming data has been read by the
-    /// application, and when all outgoing data has been ACKed by the peer.
+    /// application, and when all outgoing data has been acked by the peer.
     ///
     /// For unidirectional streams this happens when either the receive or send
     /// side is complete, depending on whether the stream was created locally
@@ -768,7 +768,7 @@
     /// Whether the stream's send-side has been shut down.
     shutdown: bool,
 
-    /// Ranges of data offsets that have been ACKed.
+    /// Ranges of data offsets that have been acked.
     acked: ranges::RangeSet,
 }
 
@@ -853,7 +853,7 @@
             self.fin_off = Some(buf.max_off());
         }
 
-        // Don't queue data that was already fully ACK'd.
+        // Don't queue data that was already fully acked.
         if self.ack_off() >= buf.max_off() {
             return Ok(());
         }
@@ -928,7 +928,7 @@
         self.max_data = cmp::max(self.max_data, max_data);
     }
 
-    /// Increments the ACK'd data offset.
+    /// Increments the acked data offset.
     pub fn ack(&mut self, off: u64, len: usize) {
         self.acked.insert(off..off + len as u64);
     }
@@ -961,7 +961,7 @@
     /// Returns true if the send-side of the stream is complete.
     ///
     /// This happens when the stream's send final size is known, and the peer
-    /// has already ACKed all stream data up to that point.
+    /// has already acked all stream data up to that point.
     pub fn is_complete(&self) -> bool {
         if let Some(fin_off) = self.fin_off {
             if self.acked == (0..fin_off) {
@@ -986,7 +986,7 @@
         }
     }
 
-    /// Returns the highest contiguously ACKed offset.
+    /// Returns the highest contiguously acked offset.
     fn ack_off(&self) -> u64 {
         match self.acked.iter().next() {
             // Only consider the initial range if it contiguously covers the