add configure check for non-POSIX compliant getnameinfo signature

- glibc < 2.14 uses "unsigned" instead of "int" for flags
- openbsd and freebsd use "size_t" instead of socklen_t for servlen
  and nodelen, while still using socklen_t for salen.

closes #430

src/core.h

@@ -109,7 +109,7 @@ typedef int (*getaddrinfo_t)(const char *, const char *, const struct addrinfo *
 			     struct addrinfo **);
 
 typedef int (*getnameinfo_t) (const struct sockaddr *, socklen_t, char *, 
-			      socklen_t, char *, socklen_t, int);
+			      GN_NODELEN_T, char *, GN_SERVLEN_T, GN_FLAGS_T);
 
 typedef ssize_t (*sendto_t) (int sockfd, const void *buf, size_t len, int flags,
 			     const struct sockaddr *dest_addr, socklen_t addrlen);

src/libproxychains.c

@@ -729,8 +729,8 @@ HOOKFUNC(void, freeaddrinfo, struct addrinfo *res) {
 }
 
 HOOKFUNC(int, getnameinfo, const struct sockaddr *sa, socklen_t salen,
-	           char *host, socklen_t hostlen, char *serv,
-	           socklen_t servlen, int flags)
+	           char *host, GN_NODELEN_T hostlen, char *serv,
+	           GN_SERVLEN_T servlen, GN_FLAGS_T flags)
 {
 	INIT();
 	PFUNC();