Fix struct comparison in tests for Win64

On 64-bit Windows, sizeof(unsigned char *) is 8, sizeof(long) is 4 and
alignof(ogg_int64_t) is 8. This results in a 4-byte hole in ogg_packet
after "long e_o_s", which means ogg_packet structs cannot be reliably
compared by memcmp. Compare ogg_packet structs member-by-member instead.

This fixes `make check` for me on mingw-w64/GCC.

Signed-off-by: Ralph Giles <giles@thaumas.net>
diff --git a/src/framing.c b/src/framing.c
index 6f63ab2..79fc715 100644
--- a/src/framing.c
+++ b/src/framing.c
@@ -1493,6 +1493,34 @@
                        1,
                        0};
 
+int compare_packet(const ogg_packet *op1, const ogg_packet *op2){
+  if(op1->packet!=op2->packet){
+    fprintf(stderr,"op1->packet != op2->packet\n");
+    return(1);
+  }
+  if(op1->bytes!=op2->bytes){
+    fprintf(stderr,"op1->bytes != op2->bytes\n");
+    return(1);
+  }
+  if(op1->b_o_s!=op2->b_o_s){
+    fprintf(stderr,"op1->b_o_s != op2->b_o_s\n");
+    return(1);
+  }
+  if(op1->e_o_s!=op2->e_o_s){
+    fprintf(stderr,"op1->e_o_s != op2->e_o_s\n");
+    return(1);
+  }
+  if(op1->granulepos!=op2->granulepos){
+    fprintf(stderr,"op1->granulepos != op2->granulepos\n");
+    return(1);
+  }
+  if(op1->packetno!=op2->packetno){
+    fprintf(stderr,"op1->packetno != op2->packetno\n");
+    return(1);
+  }
+  return(0);
+}
+
 void test_pack(const int *pl, const int **headers, int byteskip,
                int pageskip, int packetskip){
   unsigned char *data=_ogg_malloc(1024*1024); /* for scripted test cases only */
@@ -1601,7 +1629,7 @@
               ogg_stream_packetout(&os_de,&op_de); /* just catching them all */
 
               /* verify peek and out match */
-              if(memcmp(&op_de,&op_de2,sizeof(op_de))){
+              if(compare_packet(&op_de,&op_de2)){
                 fprintf(stderr,"packetout != packetpeek! pos=%ld\n",
                         depacket);
                 exit(1);