PPC: [interpreter] Add basic framework for bytecode handler code generation.

PPC: [interpreter] Add basic framework for bytecode handler code generation.

Port 7877c4e0c77b5c2b97678406eab7e9ad6eba4a4d

Original commit message:
    Adds basic support for generation of interpreter bytecode handler code
    snippets. The InterpreterAssembler class exposes a set of low level,
    interpreter specific operations which can be used to build a Turbofan
    graph. The Interpreter class generates a bytecode handler snippet for
    each bytecode by assembling operations using an InterpreterAssembler.

    Currently only two simple bytecodes are supported: LoadLiteral0 and Return.

R=rmcilroy@chromium.org, dstence@us.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1250723003

Cr-Commit-Position: refs/heads/master@{#29822}