libsndfile: Add dependency on BR2_LARGEFILE

libsndfile requires sizeof(sf_count_t) == 8, where sf_count_t is a
typedef alias for off_t. This is not true by default for all
tool-chains, which leads to a runtime assert failure in binaries
compiled against libsndfile. See:

  http://permalink.gmane.org/gmane.comp.audio.libsndfile.devel/229



Add a dependency on BR2_LARGEFILE for libsndfile, and a comment if
BR2_LARGEFILE is not selected.

[Thomas: rebased patch, added more propagation of the new
BR2_LARGEFILE dependency to gst-plugins-good and mpd.]

Signed-off-by: Ryan Mallon <rmallon@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>