MIPS: Support all fast elements kinds in the major array operations. Currently missing support for unshift.

Port r12969 (b10320d7)

BUG=
TEST=

Review URL: https://chromiumcodereview.appspot.com/11412120

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13022 ce2b1a6d-e550-0410-aec6-3dcde31c8c00