remove deprecated flag string.str and string.rstr or rename it string.find()
have these functions been deprecated because of their names?
they're very useful functions, for example strstr returns an unowned string null if it doesn't find the occurrence, which it doesn't do
var str = "hello world";
unowned string ptr = str.offset(str.index_of("find"));
// ptr is not null
unowned string ptr = str.str("find");
// ptr is null
perhaps we could rename .str to .find and .rstr to .find_last
https://docs.gtk.org/glib/func.strrstr.html g_strrstr is not deprecated either