Fix endianness detection in nxt_websocket_header_t.

The nxt_websocket_header_t structure defines the layout of a websocket
frame header.  As the websocket frame is mapped directly onto this
structure its layout needs to match how it's coming off the network.

The network being big endian means on big endian systems the structure
layout can simply match that of the websocket frame header.  On little
endian systems we need to reverse the two bytes.

This was done via the BYTE_ORDER, BIG_ENDIAN and LITTLE_ENDIAN macros,
however these are not universal, e.g they are _not_ defined on illumos
(OpenSolaris / OpenIndiana) and so we get the following compiler errors

In file included from src/nxt_h1proto.c:12:0:
src/nxt_websocket_header.h:25:13: error: duplicate member 'opcode'
     uint8_t opcode:4;
             ^~~~~~
src/nxt_websocket_header.h:26:13: error: duplicate member 'rsv3'
     uint8_t rsv3:1;
             ^~~~
src/nxt_websocket_header.h:27:13: error: duplicate member 'rsv2'
     uint8_t rsv2:1;
             ^~~~
src/nxt_websocket_header.h:28:13: error: duplicate member 'rsv1'
     uint8_t rsv1:1;
             ^~~~
src/nxt_websocket_header.h:29:13: error: duplicate member 'fin'
     uint8_t fin:1;
             ^~~
src/nxt_websocket_header.h:31:13: error: duplicate member 'payload_len'
     uint8_t payload_len:7;
             ^~~~~~~~~~~
src/nxt_websocket_header.h:32:13: error: duplicate member 'mask'
     uint8_t mask:1;
             ^~~~

This commit fixes that by using the new NXT_HAVE_{BIG,LITTLE}_ENDIAN
macros introduced in the previous commit.

Closes: <#297>
Fixes: e501c74 ("Introducing websocket support in router and libunit.")
Reviewed-by: Alejandro Colomar <alx@nginx.com>
Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

Author: ac000

src/nxt_websocket_header.h

@@ -10,7 +10,7 @@
 
 
 typedef struct {
-#if (BYTE_ORDER == BIG_ENDIAN)
+#if (NXT_HAVE_BIG_ENDIAN)
     uint8_t fin:1;
     uint8_t rsv1:1;
     uint8_t rsv2:1;
@@ -21,7 +21,7 @@ typedef struct {
     uint8_t payload_len:7;
 #endif
 
-#if (BYTE_ORDER == LITTLE_ENDIAN)
+#if (NXT_HAVE_LITTLE_ENDIAN)
     uint8_t opcode:4;
     uint8_t rsv3:1;
     uint8_t rsv2:1;