PPC: [runtime] Replace COMPARE/COMPARE_STRONG with proper Object::Compare.

PPC: [runtime] Replace COMPARE/COMPARE_STRONG with proper Object::Compare.

Port 593c655a3c814277283f9fa1520d5ce59d6b019c

Original commit message:
    This removes the weird COMPARE and COMPARE_STRONG JavaScript builtins
    and replaces them with a proper C++ implementation in Object::Compare
    and appropriate wrappers Object::LessThan, Object::GreaterThan, and
    friends that are intended to be used by a true/false returning CompareIC
    in the future, as well as the interpreter.  As a short-term solution we
    provide %Compare and %Compare_Strong entry points for the current
    CompareIC that return the appropriate integer values expected by
    fullcodegen currently.

    Now the Abstract Relational Comparison is also using the correct
    ToPrimitive implementation, which properly supports @@toPrimitive.

R=bmeurer@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, dstence@us.ibm.com
BUG=v8:4307
LOG=n

Review URL: https://codereview.chromium.org/1356983002

Cr-Commit-Position: refs/heads/master@{#30836}