allow quoted-insert while reading readline search strings; force filename argument to enable -f without a slash to read from the current directory; update BASH_LOADABLES_PATH documentation

lib/sh/compat.c

@@ -45,3 +45,9 @@ legal_alias_name (const char *string, int flags)
 {
   return (valid_alias_name (string, flags));
 }
+
+int
+compat_init (void)
+{
+  return 0;
+}