Reviewed by Adam Roben.

        Fix crashes on ARM due to different struct packing. Based on a patch
        by Mike Emmel.
        * kjs/ustring.cpp: compile-time assert to make sure sizeof(UChar) == 2
        * kjs/ustring.h: pack UChar struct to ensure that sizeof(UChar) == 2
        * wtf/Assertions.h: add COMPILE_ASSERT macro for compile-time assertions

  WebCore:

        Reviewed by Adam Roben.

        Fix crashes on ARM due to different struct packing. Based on a patch
        from Mike Emmel.

        * platform/DeprecatedString.cpp: compile-time assert to make sure sizeof(DeprecatedChar) == 2
        * platform/DeprecatedString.h: pack DeprecatedChar struct to ensure that
        sizeof(DeprecatedChar) == 2. Move _internalBuffer in DeprecatedStringData
        to the end, to avoid crashes on ARM due to different struct packing.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@19679 268f45cc-cd09-0410-ab3c-d52691b4dbfc