Include <netinet/in.h> in omrsock.h

This header is responsible for defining the in6_addr struct. This type
is used in the header <netinet/tcp.h>. On some versions of AIX, tcp.h
does not include in.h (despite using types defined there), so we have to
manually include it before tcp.h. This isn't a problem on other posix
platforms.

Fixes: #5360
Signed-off-by: Robert Young <rwy0717@gmail.com>

port/unix_include/omrsock.h

@@ -40,6 +40,7 @@
 
 #include <sys/types.h> /* Some historical implementations need this file, POSIX.1-2001 does not. */
 #include <sys/socket.h>
+#include <netinet/in.h> /* Must come before <netinet/tcp.h> */
 #include <netinet/tcp.h>
 
 typedef struct sockaddr omr_os_sockaddr;