[WIN] Remove remaining calls to pthread from WTF
https://bugs.webkit.org/show_bug.cgi?id=114563

Reviewed by Brent Fulgham.

Replace pthread_key_create with threadSpecificKeyCreate and
pthread_setspecific with threadSpecificSet from ThreadSpecific.h.
These functions provide a windows-specific implementation for the pthread functions,
but require that the thread has been created with WTF::createThread(),
which is the case for all threads created within WebKit.
To call this function from fastMalloc we must not call fastMalloc in them.
To fulfill this constraint ThreadSpecificWin will allocated its memory through the
original malloc implementation and use the stack for local and static variables.
Keep the Darwin implementation as it is, since it contains some performance tweaks.

* wtf/FastMalloc.cpp:
* wtf/ThreadSpecificWin.cpp:
(WTF::destructorsList):
(WTF::destructorsMutex):
(WTF::threadSpecificKeyCreate):
(WTF::threadSpecificKeyDelete):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@148462 268f45cc-cd09-0410-ab3c-d52691b4dbfc