Refactor audio conversion functions.

Use a consistent naming scheme that can be understood at the callsite
without having to refer to documentation.

Remove hacks in AudioBuffer intended to maintain bit-exactness with the
float path. The conversions etc. are now all natural, and instead we
enforce close but not bit-exact output between the two paths.

Output of ApmTest.Process:,,

Review URL:

git-svn-id: 4adac7df-926f-26a2-2b94-8c16560cd09d
11 files changed