Move frame_id_build_unavailable_stack static

frame_id_build_unavailable_stack is only used in frame.c, so make it static.

gdb:

2017-07-28  Yao Qi  <yao.qi@linaro.org>

	* frame.c (frame_id_build_unavailable_stack): Move it up.
	* frame.h (frame_id_build_unavailable_stack): Remove the declaration.
diff --git a/gdb/frame.c b/gdb/frame.c
index 7307ec4..b4e1df4 100644
--- a/gdb/frame.c
+++ b/gdb/frame.c
@@ -485,6 +485,22 @@
   return frame;
 }
 
+/* Construct a frame ID representing a frame where the stack address
+   exists, but is unavailable.  CODE_ADDR is the frame's constant code
+   address (typically the entry point).  The special identifier
+   address is set to indicate a wild card.  */
+
+static struct frame_id
+frame_id_build_unavailable_stack (CORE_ADDR code_addr)
+{
+  struct frame_id id = null_frame_id;
+
+  id.stack_status = FID_STACK_UNAVAILABLE;
+  id.code_addr = code_addr;
+  id.code_addr_p = 1;
+  return id;
+}
+
 /* Compute the frame's uniq ID that can be used to, later, re-find the
    frame.  */
 
@@ -619,19 +635,6 @@
 /* See frame.h.  */
 
 struct frame_id
-frame_id_build_unavailable_stack (CORE_ADDR code_addr)
-{
-  struct frame_id id = null_frame_id;
-
-  id.stack_status = FID_STACK_UNAVAILABLE;
-  id.code_addr = code_addr;
-  id.code_addr_p = 1;
-  return id;
-}
-
-/* See frame.h.  */
-
-struct frame_id
 frame_id_build_unavailable_stack_special (CORE_ADDR code_addr,
 					  CORE_ADDR special_addr)
 {
diff --git a/gdb/frame.h b/gdb/frame.h
index d5800b7..d75a72d 100644
--- a/gdb/frame.h
+++ b/gdb/frame.h
@@ -198,12 +198,6 @@
 
 /* Construct a frame ID representing a frame where the stack address
    exists, but is unavailable.  CODE_ADDR is the frame's constant code
-   address (typically the entry point).  The special identifier
-   address is set to indicate a wild card.  */
-extern struct frame_id frame_id_build_unavailable_stack (CORE_ADDR code_addr);
-
-/* Construct a frame ID representing a frame where the stack address
-   exists, but is unavailable.  CODE_ADDR is the frame's constant code
    address (typically the entry point).  SPECIAL_ADDR is the special
    identifier address.  */
 extern struct frame_id