Add CMake build system files (incomplete)

This ports most of configure to CMake. Some parts (like CoreAudio
and Apple Remote on OS X) are still missing.

Probably breaks stuff left and right due to lack of testing.
cmake/mpv/Utils: Fix static linking option
CMake: Fix dsound option
CMake: Fix timer-win2.c typo
CMake: Add MinGW-specific definitions
CMake: Fix socket lib checks on Win32
CMake: PortAudio wants pthreads
CMake: Fix static linking of libquvi
CMake: Fix static linking of libbluray
CMake: Add missing lib on Win32
CMake: Fail with more descriptive error on unset CPU arch
Add CMake cross-compilation howto
CMake: Fix FindOSS

Also use a preprocessor macro to store the path to soundcard.h
timer-linux: Remove use of obsolete usleep