When building for Windows, pthreads should not be required.

[Andarwinux]

Little-CMS/plugins/threaded/include/lcms2_threaded.h

Lines 27 to 29 in 04ace9c

	#ifdef CMS_NO_PTHREADS
	#error "This plug-in needs pthreads to operate"
	#endif

LCMS uses the Win32 API directly instead of pthread, so why the hard error here? If I remove this check, I can still build LCMS withthread plugin without pthread.