Fixes http://bugs.musicpd.org/view.php?id=4432

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.

For type safety and code readability.

Prepare to migrate away from GLib.  Currently, we're still using GLib
as a backend.

Replaces GLib's GError.

Cast to integer after multiplying with 1000.  Allows sub-second
seeking.

Pass a callback table to scan_file() and scan_stream(), instead of
returning a tag object.

When gme_track_info() returns with success, then the gme_info_t
pointer must be set.

this needs to be done for the end of songs to be detected.