PPC: perf enhancement: optimize code patching sync sequences.
PPC: perf enhancement: use group-ending nops to minimize LHS penalty.

Placing this nop between a store instruction followed by a load from
the same address (used for transfering values between floating point
and general purpose registers) should minimize the Load-Hit-Store
(LHS) penalty.
PPC: perf enhancement: clean up store-with-update usage.
PPC: perf enhancement: improve CopyCharsUnsigned non-conversion cases.
PPC: perf enhancement: improve prologue performance.

Pass code entry address in ip for use by constant pool pointer
initialization and code aging logic.

Conflicts:

	src/ppc/code-stubs-ppc.cc
PPC: perf enhancement: use bctrl for calls (vs blrl).