Fixup whitespace formatting
h264parse: Get correct value for NAL unit size after first NAL unit in a buffer

When inserting start codes into buffers containing multiple NAL units, the
size of the first NAL unit in the buffer was used as the size for every
NAL unit in the buffer.  Update the algorithm to properly parse each NAL units
size from the input buffer.
Don't check for picture_start before inserting SPS/PPS when outputting AU

When merging output into AU buffers, each buffer will by definition
be the start of picture.  This additional check is not only unnecessary, it
will push the SPS/PPS into the second buffer, which is incorrect.