Parse the R128_TRACK_GAIN comment string.

Call decoder_timestamp().  This is not necessary currently, but will
be as soon as we implement seeking.

This requires seeking to the end-of-stream, checking its granulepos,
and then seeking back to the previous file position.  We do this only
for local files.

Eliminate the temporary buffer, do I/O right into the WritableBuffer.

Replaces GLib's g_ascii_strncasecmp().

Replaces GLib's g_ascii_strcasecmp().

The "loop_count" configuration parameter allows the user to set how
many times a module with backward loops shall loop. "0" (the default)
means a module is not allowed to use backward loops at all. "-1"
enables inifinite looping.

This patch allows the user to configure the mikmod decoder plugin to loop
modules. It adds a configuration parameter to the mikmod decoder called
"loop" which can be "no" (the old behaviour, default) or "yes" to allow
modules to use backward loops.

The new class Path only holds a string pointer without being
responsible for allocation/deallocation.  The FileSystem.hxx library
accepts Path arguments instead of AllocatedPath, to avoid forcing
callers to allocate another string object.

Decouple some more from GLib.

Replacing GLib macros.