All macro-assembler-*.cc used a number of common enums. Moved these to macro-assembler.h.

Removed unused enum ExitJSFlag from ARM macro assembler.
Review URL: http://codereview.chromium.org/202004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2836 ce2b1a6d-e550-0410-aec6-3dcde31c8c00