API: add a generic value type.

Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>
API: rename H.264 encoding buffer structs with a Baseline suffix.

Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>
API: drop H.264 specific VA buffer types.

VAEncH264VUIBufferType and VAEncH264SEIBufferType were never used
in any driver. Besides, they are codec-specific which is against
the generic buffer type policy. A new scheme will be developed.

Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>
API: add new H.264 encoding API for main and high profiles.

Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>
API: h264 encode: re-define packed-headers buffer type ids.
API: h264 encode: rename insert_emulation_bytes to has_emulation_bytes.
API: h264 encode: add macroblock parameter buffer.
API: h264 encode: add new config attributes for encoding (max-ref-frames).
API: h264 encode: improve VA config attributes documentation.
API: h264 encode: renumber config attributes used for encoding.
API: h264 encode: add new VA config attributes (max-slices, slice-structure).
API: h264 encode: fix comments.
API: h264 encode: add constant QP rate control attribute.
API: h264 encode: remove TABs in newly added code.
API: h264 encode: add max-frame-size misc buffer type.
API: h264 encode: fix max-frame-size parameter buffer type.
API: h264 encode: add macroblock-info config attribute.
API: h264 encode: add packed SEI header.
API: h264 encode: fix VAConfigAttribEncMaxRefFrames semantics.
API: h264 encode: add VA_RC_VBR_CONSTRAINED.