Remove option to use socks5 library

This was always disabled by default and is not required
for the current socks support. I am not even sure this
library is packaged by any distro?

src/common/util.c

@@ -51,9 +51,6 @@
 #if defined (USING_FREEBSD) || defined (__APPLE__)
 #include <sys/sysctl.h>
 #endif
-#ifdef SOCKS
-#include <socks.h>
-#endif
 
 /* SASL mechanisms */
 #ifdef USE_OPENSSL