Coverity: No effect: CID 598

Coverity: No effect: CID 598

	* src/media/media-mad.c (media_mad_open): Use long for result of
	ftell. Previous use of size_t could cause a bad ftell to be
	considered a maximum size media file... Later the positive size has
	to be cast to size_t for storage in the structure.

Signed-off-by: Nelson Ferreira <nelson.ferreira@ieee.org>