Fix a buffer overflow in libx264 interface to x264 encoder. Previous code ignored the compressed buffer size passed in. This change returns as many complete NALs as can fit in the buffer, and logs an error message.

Signed-off-by: Mike Scheutzow <mike.scheutzow@alcatel-lucent.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
