merge from stable branch:
  1.46.4.3  +14 -7     fptools/ghc/compiler/nativeGen/AsmCodeGen.lhs
  1.47.4.3  +2 -0      fptools/ghc/compiler/nativeGen/MachMisc.lhs

  Treat literal appearances of BaseReg in Stix trees uniformly.
  This is now taken to mean the &MainCapability.r, regardless of
  whether BaseReg is in a register (x86) or synthesised (sparc).