Pre-generate Bison parser files in Repo

[dgovil]

Problem

OSL builds currently generate the Bison parser code during their builds. It would be really great if someone could pre-generate these files and include them in the repo for the build system to use.

This would allow reducing the dependency count in OSL on Windows/Mac to not require bison on each machine, and would make builds ever so slightly more efficient for each builder.

This would require adjusting:

• src/liboslexec/CMakeLists.txt, src/liboslquery/CMakeLists.txt and src/liboslcomp/CMakeLists.txt to allow using the pre-generated files.
• INSTALL.md and the various platform doc/build_install/windows/Readme.md files that mention requiring bison, to making it optional.
• doc/build_install/windows/build_osl.py to make bison an optional build component.