MIPS: Add big-endian support for MIPS.

Important notices:

- The snapshot cannot be created for big-endian target in cross-compilation
  environment on little-endian host using simulator.

- In order to have i18n support working on big-endian target, the icudt46b.dat and
  icudt46b_dat.S files should be generated and upstreamed to ICU repo.

- The mjsunit 'nans' test is endian dependent, it is skipped for mips target.

- The zlib and Mandreel from Octane 2.0 benchmark are endian dependent due to
  use of typed arrays.

TEST=
BUG=
R=jkummerow@chromium.org, plind44@gmail.com

Review URL: https://codereview.chromium.org/228943009

Patch from Dusan Milosavljevic <Dusan.Milosavljevic@rt-rk.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20778 ce2b1a6d-e550-0410-aec6-3dcde31c8c00