winxp threads: detect SRWLock emulation reentrancy

winxp threads: detect SRWLock emulation reentrancy

We lack SRWLock on Windows XP, so we use CRITICAL_SECTION to emulate it
there.  SRWLock is non-recursive, but CRITICAL_SECTION will happily
allow itself to be acquired multiple times by the same thread.

We need to detect if our second acquire succeeded because of the
recursive nature of CRITICAL_SECTION.  In the case of a _lock()
operation, we would normally have deadlocked, so abort.  In the case of
a _trylock() operation, we need to ensure that FALSE is properly
returned.

Problem caught by Matthias Clasen and Chun-wei Fan.

https://bugzilla.gnome.org/show_bug.cgi?id=660096