patch courtesy of Todd Kirby:

* Fixes a small memory leak in read_rle_sgi()
* Remove temp buffer in read_rle_sgi(). Write rle data directly to image
buffer.
* Adds sanity check to read_rle_sgi() to insure decoded rle data row
equals image width.

Originally committed as revision 2993 to svn://svn.ffmpeg.org/ffmpeg/trunk