Win32: rework mutex/condition implementation.

Win32: rework mutex/condition implementation.

Get rid of unsafe PulseEvent().
Fix recursive mutex implementation (hopefully).
Use critical section (fast non-shared/intra-process mutexes)
 rather than mutex handle (slow shared/inter-process mutexes) [1].
Do not rely on unspecified locking when SignalObjectAndWait is alerted.
Real vlc_cond_broadcast() support (hopefully).

[1] should also merge the WinCE support with WinNT.