Fix OBU related MSVC and x86 build warnings.
Fix OBU related MSVC and x86 build warnings.

Some missing casts for the most part. Made a couple
type changes where appropriate. Added range checks
in circumstances where we must support storage of
a potentially larger than 32-bit value in a 32-bit
type.

Change-Id: I8275dc9d65fd5d7fb95054d0ce5be61b0e558887

GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom