Port bd732f7d

Original Commit Message:

    The original CL introduced a test which uses a random number generator.
    I disable the test for now, which is okay because this CL adds to a
    work-in-progress feature anyways, and I will fix the problem in another
    CL.

    Original description:
    Add the ability to return (multiple) return values on the stack:

    - Extend stack frames with a new buffer region for return slots.
      This region is located at the end of a caller's frame such that
      its slots can be indexed as caller frame slots in a callee
      (located beyond its parameters) and assigned return values.
    - Adjust stack frame constructon and deconstruction accordingly.
    - Extend linkage computation to support register plus stack returns.
    - Reserve return slots in caller frame when respective calls occur.
    - Introduce and generate architecture instructions ('peek') for
      reading back results from return slots in the caller.
    - Aggressive tests.
    - Some minor clean-up.

    So far, only ia32 and x64 are implemented.

R=ahaas@chromium.org, joransiu@ca.ibm.com, jbarboza@ca.ibm.com
BUG=
LOG=N

Change-Id: I8d63286aa5af5f52cc2eeaf2adeee13d0ff19e7d
Reviewed-on: https://chromium-review.googlesource.com/823084
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Reviewed-by: Joran Siu <joransiu@ca.ibm.com>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50091}