Fix -Werror=cast-align error on 32 bit platform

Fixes GH-172

android-config

@@ -39,6 +39,7 @@ PATH=$TOOLCHAIN/bin:$PATH
     --without-libxml2 \
     --disable-python-bindings \
     --disable-examples \
+    --enable-werror \
     CC=clang \
     CXX=clang++ \
     CPPFLAGS="-I$PREFIX/include" \

configure.ac

@@ -549,6 +549,10 @@ if test "x$have_struct_tm_tm_gmtoff" = "xyes"; then
             [Define to 1 if you have `struct tm.tm_gmtoff` member.])
 fi
 
+# Check size of pointer to decide we need 8 bytes alignment
+# adjustment.
+AC_CHECK_SIZEOF([int *])
+
 # Checks for library functions.
 if test "x$cross_compiling" != "xyes"; then
   AC_FUNC_MALLOC

lib/nghttp2_map.h

@@ -40,6 +40,10 @@ typedef uint32_t key_type;
 typedef struct nghttp2_map_entry {
   struct nghttp2_map_entry *next;
   key_type key;
+#if SIZEOF_INT_P == 4
+  /* we requires 8 bytes aligment */
+  int64_t pad;
+#endif
 } nghttp2_map_entry;
 
 typedef struct {

lib/nghttp2_stream.c

@@ -119,6 +119,7 @@ static int stream_push_item(nghttp2_stream *stream, nghttp2_session *session) {
     }
     break;
   default:
+    rv = 0;
     /* should not reach here */
     assert(0);
   }