Merged r13230, r13258 into 3.15 branch.

MIPS: Improve array to string conversion.

MIPS: ARM: fix a bug with saving lr register in GenerateSmiToDouble.

R=mstarzinger@chromium.org

Review URL: https://chromiumcodereview.appspot.com/11878019

git-svn-id: https://v8.googlecode.com/svn/branches/3.15@13373 ce2b1a6d-e550-0410-aec6-3dcde31c8c00