test: intrapred harness fixup
csv: improve CSV headers to use title caps
api: change x265_param.bpyramid to bBPyramid (bool)

x264's strict bpyramid mode seems to be H.264/blue-ray specific and thus we are
left with only on or off.
api: add alloc/free methods for x265_param

This allows apps to use x265_param as pure abstract structures, just like
x265_encoder, in order to make their app future-safe against changes to
x265_param (without requiring recompiles or code changes).
api: add alloc/free methods for x265_picture for future safety
Merge with stable