MIPS: Implement in-heap backing store for typed arrays.

Port r18651 (49744859)

Original commit message:
This adds a fixed array sub-type that will represent a backing store for
typed arrays allocated with TypedArray(length) construtor.

BUG=
R=plind44@gmail.com

Review URL: https://codereview.chromium.org/141143003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18652 ce2b1a6d-e550-0410-aec6-3dcde31c8c00