Improve code generation for array-like accessors when offset is constant.
Improve code generation for array-like accessors when offset is constant.

froggey/Mezzano,AugustusHuang/Mezzano,varjagg/Mezzano,varjagg/Mezzano,AugustusHuang/Mezzano,froggey/Mezzano,rvedam/Mezzano,rvedam/Mezzano