[sh4] Prepare baseline JIT for DFG_JIT implementation.

[sh4] Prepare baseline JIT for DFG_JIT implementation.
https://bugs.webkit.org/show_bug.cgi?id=119758

Patch by Julien Brianceau <jbrianceau@nds.com> on 2013-08-13
Reviewed by Oliver Hunt.

* assembler/MacroAssemblerSH4.h:
    - Introduce a loadEffectiveAddress function to avoid code duplication.
    - Add ASSERTs and clean code.
* assembler/SH4Assembler.h:
    - Prepare DFG_JIT implementation.
    - Add ASSERTs.
* jit/JITStubs.cpp:
    - Add SH4 specific call for assertions.
* jit/JITStubs.h:
    - Cosmetic change.
* jit/JITStubsSH4.h:
    - Use constants to be more flexible with sh4 JIT stack frame.
* jit/JSInterfaceJIT.h:
    - Cosmetic change.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@154016 268f45cc-cd09-0410-ab3c-d52691b4dbfc