Add #include <sys/socket.h> to xcb_conn.c

Solves compiler warning on Solaris:
"xcb_conn.c", line 304: warning: implicit function declaration: shutdown

Also provides system definition of SHUT_RDWR on Solaris 11.

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Reviewed-by: Jamey Sharp <jamey@minilop.net>

src/xcb_conn.c

@@ -44,6 +44,7 @@
 #ifdef _WIN32
 #include "xcb_windefs.h"
 #else
+#include <sys/socket.h>
 #include <netinet/in.h>
 #endif /* _WIN32 */