Add "replacement" argument for string_remove_color in plugin API

src/core/wee-string.c

@@ -1309,13 +1309,3 @@ string_format_size (unsigned long size)
     
     return strdup (str_size);
 }
-
-/*
- * string_remove_color: remove WeeChat color codes in string
- */
-
-char *
-string_remove_color (const char *string)
-{
-    return (char *)gui_color_decode ((unsigned char *)string);
-}