Fixed a bug in CopyBytes() and new test cases for ARM macro assembler

TEST=cctest/test-macro-assembler-arm
R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/23447035

Patch from Bangfu Tao <bangfu.tao@samsung.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16873 ce2b1a6d-e550-0410-aec6-3dcde31c8c00