basic: introduce socket_protocol_{from,to}_name()

And use them where they can be applicable.

src/basic/socket-protocol-to-name.awk

@@ -0,0 +1,9 @@
+BEGIN{
+        print "static const char* const socket_protocol_names[] = { "
+}
+!/HOPOPTS/ {
+        printf "        [IPPROTO_%s] = \"%s\",\n", $1, tolower($1)
+}
+END{
+        print "};"
+}