mutex subsystem, -V9

this is version -V9 of the generic mutex subsystem. It consists of the following 13 patches:

add-atomic-xchg.patch
mutex-generic-asm-implementations.patch
mutex-asm-mutex.h-i386.patch
mutex-asm-mutex.h-x86_64.patch
mutex-asm-mutex.h-arm.patch
mutex-arch-mutex-h.patch
mutex-core.patch
mutex-docs.patch
mutex-debug.patch
mutex-debug-more.patch
xfs-use-mutexes.patch
vfs-i-sem-to-mutex.patch
vfs-use-more-mutexes.patch

the patches are against Linus' latest GIT tree, and they should work fine on every Linux architecture.

i have tested all 5 mutex implementation variants under MUTEX_DEBUG_FULL on x86: native, -dec, -xchg, -null and debug.

Changes since -V8:

 93 files changed, 502 insertions(+), 500 deletions(-)

- ARMv6: __mutex_fastpath_trylock micro-optimization (Nicolas Pitre)

- asm-generic/mutex-xchg.h: better __mutex_fastpath_trylock implementation (Nicolas Pitre)

- XFS: use mutexes directly (Jes Sorensen)

- experimental conversion of VFS: change i_sem to i_mutex (Jes Sorensen)

Ingo