Enable code generation for array literals....

Enable code generation for array literals.

Introduce macro assembler support for pushing heap-object handles and
for comparing a register to a heap-object handle.

Cleanup: Remove some code that was needlessly commented out.  Added
TODO's for code that was commented out (where we do not hit an
UNIMPLEMENTED). 

Committed: http://code.google.com/p/v8/source/detail?r=2241

[William Hesse, 2009-06-22 15:05:24]

Merge changes in macroassembler-x64 with changes from r2238 (Move and Cmp
added).
LGTM.