Add two more failing test cases based on avconv.c.
Add two more failing test cases based on avconv.c.

mstorsjo/c99-to-c89,mstorsjo/c99-to-c89,rbultje/c99-to-c89,libav/c99-to-c89,rbultje/c99-to-c89,libav/c99-to-c89