Replaces GLib's g_strsplit().

Use simple string and path parsing functions instead of GLib's
g_pattern_match(), which was used in a very clumsy way.

There is duplicate code in the two.

Prepare for a ICU-based backend without GLib.

Don't expose pointer that requires the caller to invoke g_free(),
because that's GLib-only.

Don't abort the process, let the caller decide instead.