- Exclude platform-specific includes (anything in < >) from the
clang preprocessor by using `!defined(GENERATING_CEF_API_HASH)`
in CEF header files.
- Define "target platforms" by passing platform- and architecture-
specific ifdefs to the clang preprocessor. Grep for `defined(OS_`
to identify headers that require target platform processing, and
then process for each target as the platform-specific API hash
contribution.
- Delete the univeral hash which is no longer a useful concept.
