replace spinlock by QemuMutex.

replace spinlock by QemuMutex.

spinlock is only used in two cases:
  * cpu-exec.c: to protect TranslationBlock
  * mem_helper.c: for lock helper in target-i386 (which seems broken).

It's a pthread_mutex_t in user-mode, so we can use QemuMutex directly,
with an #ifdef.  The #ifdef will be removed when multithreaded TCG
will need the mutex as well.

Signed-off-by: KONRAD Frederic <[email protected]>
Message-Id: <1439220437[email protected]>
Signed-off-by: Emilio G. Cota <[email protected]>
[Merge Emilio G. Cota's patch to remove volatile. - Paolo]
Signed-off-by: Paolo Bonzini <[email protected]>