PPC: perf enhancement: optimize LeaveFrame.

Conflicts:

	src/ppc/builtins-ppc.cc
	src/ppc/code-stubs-ppc.cc
	src/ppc/lithium-codegen-ppc.cc
PPC: perf enhancement: optimize Allocate.
PPC: perf enhancement: optimize AddAndCheckForOverflow when rhs is an immediate value.
PPC: perf enhancement: detect recursive calls.
Work around gcc compiler bug.