MIPS: [Interpreter] Add ForInPrepare runtime function which returns a ObjectTriple.

MIPS: [Interpreter] Add ForInPrepare runtime function which returns a ObjectTriple.

Port for https://codereview.chromium.org/1576093004/

Original commit message:
Adds a ForInPrepare Runtime function which returns a triple of
cache_type, cache_array and cache_length.

This requires adding support to CEntryStub to call runtime functions
which return a ObjectTriple - a struct containing three Object*
pointers. Also did some cleanup of the x64 CEntryStub to avoid
replicated code.

Replaces the interpreter's use of the ad-hock InterpreterForInPrepare
Runtime function with ForInPrepare in preparation for fixing deopt in
BytecodeGraphBuilder for ForIn (which will be done in a followup CL).

BUG=v8:4280
LOG=N

[balazs.kilvady, 2016-01-14 17:43:05]

balazs.kilvady@imgtec.com changed reviewers:
+ akos.palfi@imgtec.com, ivica.bogosavljevic@imgtec.com, paul.lind@imgtec.com,
rmcilroy@chromium.org

[balazs.kilvady, 2016-01-14 17:43:05]

On sims we are good, on both mipsel and mip64el sim has exactly the same
failures as before aplying the ported CL.