include: Add arpa/inet.h for htonl

This should fix a build warning on FreeBSD.

Signed-off-by: Andreas Schneider <asn@cryptomilk.org>

include/libssh/priv.h

@@ -48,6 +48,10 @@
 #include <byteswap.h>
 #endif
 
+#ifdef HAVE_ARPA_INET_H
+#include <arpa/inet.h>
+#endif
+
 #ifndef bswap_32
 #define bswap_32(x) \
     ((((x) & 0xff000000) >> 24) | (((x) & 0x00ff0000) >>  8) | \