CHANGES and mark beta

CHANGES

Simplify Makefile wrapper a bit

Allow overrides of the build_dir and dist_dir.

For SPI, build debug & release libs in same place for better staging.
Also some other local build updates that won't affect anyone else.

Typo fix

Movie reader enhancement (AcademySoftwareFoundation#2349)

The original code was always asking ffmpeg to give it RGB uint8 frames.

This patch modifies it so that it asks for RGBA when alpha is present,
1-channel image when it's a greyscale movie, and retrieve as uint16
when >8 bits per channel are stored in the file.

If you are, to pick a hypothetical example at random, trying to
convert a 10 bit rgba quicktime of an fx element into individual
frames to save out as TIFF files, this will fully preserve the 10 bits
and alpha channel, whereas before you would just get back a crappy 8
bit rgb.

Also updated where the SPI build gets its ffmpeg, to pick up a newer
version.

Better CMake status messages upon config startup

Some cleanup of recent SPI-specific build scripts

Some synchronization with OSL build scripts, including making some
places that said "OpenImageIO_blah" into "${PROJECT_NAME}_blah" and
the like, for the sake of easy sharing between the projects.

build.py turns out to no longer be needed, but a new CMakeLists.txt for
the Rez distro makes downstream Rez packages happy. From Jon Ware.

SPI touchups

CHANGES

Fix not allocating enough scratch space for cmyk tiff reads

Related to the fixes I did a couple commits ago. There was one use of
a temp buffer that was allocating based on the 3-channel size for
translation to RGB, but it was being used to read the raw 4 channnel
data into it, overrunning the bounds and screwing up the heap.