Reviewed by George Staikos.

        Defines two pseudo-platforms for ARM and Thumb-2 instruction set.
        https://bugs.webkit.org/show_bug.cgi?id=29122

        Introduces WTF_PLATFORM_ARM_TRADITIONAL and WTF_PLATFORM_ARM_THUMB2
        macros on ARM platforms. The PLATFORM(ARM_THUMB2) should be used
        when Thumb-2 instruction set is the required target. The
        PLATFORM(ARM_TRADITIONAL) is for generic ARM instruction set. In
        case where the code is common the PLATFORM(ARM) have to be used.

        Modified by George Wright  <gwright@rim.com> to correctly work
        with the RVCT-defined __TARGET_ARCH_ARM and __TARGET_ARCH_THUMB
        compiler macros, as well as adding readability changes.

        * wtf/Platform.h:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@48954 268f45cc-cd09-0410-ab3c-d52691b4dbfc