fix issue 225, instead of stoping when wrong atom size is found,

fix issue 225, instead of stoping when wrong atom size is found,
limit atom size to what is left, assuming container atom has correct size..
cricket4.3g2 has incorrect moov atom size which indicates that file size should be
2 bytes bigger than it is and quicktime reads it correctly though.

Originally committed as revision 10836 to svn://svn.ffmpeg.org/ffmpeg/trunk