allow : and [ in alias names (but forbid [[ explicitly)

to make 'enable' completely work again

funcs.c

@@ -38,7 +38,7 @@
 #endif
 #endif
 
-__RCSID("$MirOS: src/bin/mksh/funcs.c,v 1.346 2017/04/27 23:18:05 tg Exp $");
+__RCSID("$MirOS: src/bin/mksh/funcs.c,v 1.347 2017/04/27 23:33:18 tg Exp $");
 
 #if HAVE_KILLPG
 /*
@@ -747,6 +747,8 @@ valid_alias_name(const char *cp)
 {
 	if (ord(*cp) == ord('-'))
 		return (false);
+	if (ord(cp[0]) == ord('[') && ord(cp[1]) == ord('[') && !cp[2])
+		return (false);
 	while (*cp)
 		if (ctype(*cp, C_ALIAS))
 			++cp;