Update to r7202

Else than the regular rebasing, I have modified the source in these ways:

- Changed all `"webrtc/typedefs.h"` to `#include "typedefs.h"`
- Removed all `webrtc/common_audio/signal_processing/include/`
- Modified typedefs.h to current upstream. Upstream has removed the original
  content in typedefs.h (before those were moved to ilbc.h), and corresponding
  content in ilbc.h is removed as well.
- Commented out CPU detection code in signal_processing/spl_init.c to make it
  build without importing the CPU library.

Some of the modifications listed above were not applied to architecture-
specific code or unit tests.
Add pthread detection

It is needed by spl_init.c.