[#491] Fix bug in binding to TCP/IP port

The problem is that the port string was created as a 5 chars, while it
can be 5 effective chars plus the string end '\0'.

Close #491

src/libpgagroal/network.c

@@ -604,7 +604,7 @@ bind_host(const char* hostname, int port, int** fds, int* length, bool non_block
    index = 0;
    size = 0;
 
-   sport = calloc(1, 5);
+   sport = calloc(1, 6);
    if (sport == NULL)
    {
       pgagroal_log_fatal("Couldn't allocate memory while binding host");