Remove support for de-facto dead archs.

src/vm_ppc.dasc

@@ -18,7 +18,6 @@
 |// DynASM defines used by the PPC port:
 |//
 |// P64     64 bit pointers (only for GPR64 testing).
-|//         Note: see vm_ppc64.dasc for a full PPC64 _LP64 port.
 |// GPR64   64 bit registers (but possibly 32 bit pointers, e.g. PS3).
 |//         Affects reg saves, stack layout, carry/overflow/dot flags etc.
 |// FRAME32 Use 32 bit frame layout, even with GPR64 (Xbox 360).