PPC: [runtime] Initial step towards switching Execution::Call to callable.

PPC: [runtime] Initial step towards switching Execution::Call to callable.

Port d5bbd45f044ae6796c0d0f7bd8732069d74418de

Original commit message:
    Currently Execution::Call (and friends) still duplicate a lot of the
    Call sequence logic that should be encapsulated in the Call and
    CallFunction builtins. So the plan now is to switch Execution::Call
    to accept any Callable and just pass that through to the Call builtin.

R=bmeurer@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, dstence@us.ibm.com
BUG=v8:4413
LOG=n

Review URL: https://codereview.chromium.org/1347213003

Cr-Commit-Position: refs/heads/master@{#30813}