util: require inet_pton()

Always use inet_pton() for converting IP addresses. It should be
available on all currently supported systems.

sysincl.h

@@ -28,6 +28,7 @@
 #ifndef GOT_SYSINCL_H
 #define GOT_SYSINCL_H
 
+#include <arpa/inet.h>
 #include <assert.h>
 #include <ctype.h>
 #include <errno.h>
@@ -61,11 +62,6 @@
 #include <sys/timex.h>
 #endif
 
-#ifdef FEAT_IPV6
-/* For inet_ntop() */
-#include <arpa/inet.h>
-#endif
-
 #ifdef HAVE_GETRANDOM
 #include <sys/random.h>
 #endif