Cleanup: Remove 100+ compiler warnings.

This is a big cleanup that removes compiler warnings by performing
the following:

- Remove unused functions or variables.
- Change pointer cast to be alias safe using unions.
- Use __attribute__((unused)) on some local variable definitions
  when their usage depends on conditional defines that are not
  always true when compiling the same source several times.
- Fix a couple array indexing bugs.

There are still a few warnings from the JSON lexer, libjpeg and
the TCG helpers though, but the overall compilation is much cleaner.

BUG=NONE

Change-Id: Ic4483e6402b266ecfd7bca8c92a73d8fcf392a1f
48 files changed