Fix endianness detection

Commit 97f442ef2a tried to improve the
endianness detection, but introduced a typo and problems for Windows
builds (no endian.h, different definition of LIBVNCSERVER_WORDS_BIGENDIAN).

Fix both issues.

Signed-off-by: Stefan Weil <sw@weilnetz.de>

rfb/rfbproto.h

@@ -80,11 +80,12 @@
 #endif
 #endif
 
+#if !defined(_WIN32)
 # include <endian.h>
 # if __BYTE_ORDER == __BIG_ENDIAN
-#  define LIBVBNCSERVER_WORDS_BIGENDIAN 1
+#  define LIBVNCSERVER_WORDS_BIGENDIAN 1
 # endif
-
+#endif /* !_WIN32 */
 
 /* MS compilers don't have strncasecmp */
 #ifdef _MSC_VER