First stab at a general ARM cleanup patch. It merges ARM constants so that they can be used across simulator, assembler and disassembler, and tidies up some syntax and ambiguities.

BUG=none
TEST=none

Review URL: http://codereview.chromium.org/6274009

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6483 ce2b1a6d-e550-0410-aec6-3dcde31c8c00