Move JavaScriptCore thread testing code to pthread specific directory

    Move JavaScriptCore thread testing code to pthread specific directory
        and remove the dependance on CoreFoundation by using WTF::HashSet.

        Reviewed by Geoff and Oliver.

        * DumpRenderTree/DumpRenderTree.xcodeproj/project.pbxproj:
        * DumpRenderTree/ForwardingHeaders/wtf/HashMap.h: Added.
        * DumpRenderTree/ForwardingHeaders/wtf/HashSet.h: Added.
        * DumpRenderTree/ForwardingHeaders/wtf/Vector.h: Added.
        * DumpRenderTree/JavaScriptThreading.h: Copied from DumpRenderTree/mac/JavaScriptThreading.h.
        * DumpRenderTree/mac/JavaScriptThreading.cpp: Removed.
        * DumpRenderTree/mac/JavaScriptThreading.h: Removed.
        * DumpRenderTree/pthreads: Added.
        * DumpRenderTree/pthreads/JavaScriptThreadingPthreads.cpp: Copied from DumpRenderTree/mac/JavaScriptThreading.cpp.
        (javaScriptThreads):
        (runJavaScriptThread):
        (startJavaScriptThreads):
        (stopJavaScriptThreads):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@28377 268f45cc-cd09-0410-ab3c-d52691b4dbfc