Catch up with src parse.y changes by jsg@:

Don't allow embedded nul characters in strings.
Fixes a pfctl crash with an anchor name containing
an embedded nul found with the afl fuzzer.

pfctl parse.y patch from and ok deraadt@

parse.y

@@ -438,6 +438,9 @@ yylex(void)
 			} else if (c == quotec) {
 				*p = '\0';
 				break;
+			} else if (c == '\0') {
+				yyerror("syntax error");
+				return (findeol());
 			}
 			if (p + 1 >= buf + sizeof(buf) - 1) {
 				yyerror("string too long");