replaced broken if-return logic for fixating rate and number
of channels that caused that modules were always (after
successful fixation of rate) played as mono (instead of
stereo) by correct one with appropiate warnings.
https://bugzilla.gnome.org/show_bug.cgi?id=619035
modplug's sndfile.h conflicts with libsndfile's sndfile.h, so
we'll access it directly using modplug/sndfile.h. Fixes#573849
Signed-off-by: David Schleef <ds@schleef.org>
Always build the modplug plugin against the system modplug library
and remove our own copy. Using the system version has advantages
if security issues or other critical bugs are found in libmodplug
and our own copy wasn't really maintained anyway.
Also our copy only contained some patches to use GLib types and functions.
Fixes bug #568837.
