gioerror: Add an API to set a literal GError from errno
@walters
Submitted by Colin Walters Link to original bug (#744533)
Description
I work on a lot of projects that end up calling into Unix APIs for a variety of reasons, and briding errno -> GError is too much typing/too verbose at each call site.
I've been using gs_set_error_from_errno() in libgsystem, but the goal is to deprecate that. Because this is such a tiny API, and useful for the many GNOME and other projects which use GLib + Unix, let's include it here.
We could convert many more callsites to a g_set_prefix_error_from_errno(), which libgsystem also has. But this is a first step.