MIPS: Tag smi-constants as smi. This also fixes code that copies holes into arrays.
MIPS: Tag smi-constants as smi. This also fixes code that copies holes into arrays.

Port r14814 (8a28ccfb)

BUG=

Review URL: https://codereview.chromium.org/16041005

git-svn-id: b158db1e4b4ab85d4c9e510fdef4b1e8c614b15b@14830 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh