* threads.c: applied Serguei Narojnyi's patch to add native
  thread support on the Win32 platform
* testThreadsWin32.c Makefile.am: added the test program also
  from Serguei, Win32 specific
* include/win32config.h include/libxml/xmlwin32version.h.in:
  added patch from Igor for the Windows thread specific defines.
Daniel