Merged following commit from v8ppc

Author: Mike Tunnicliffe <mike.tunnicliffe@uk.ibm.com>
Date:   Mon Jan 6 12:05:41 2014 -0500

    Hackish changes to improve compatibility with G4 processors
    Hacks include:
    * Instruction cache size change (probably breaks other platforms)
    * Changing v8globals.h
    * Structure of changes to avoid fcfid
    * Calling through to MathPowStub register fiddling to avoid fsqrt

    Ran this on a G4, tests no longer crash but there were failures.
    Particularly one where the square root is out by a very