----------------------------------------
	Make isFFIArgumentTy understand newtypes
	----------------------------------------

This fixes the bug Manuel reported:

	newtype T = T (Ptr T)
	foreign import ccall foo :: T -> IO (Ptr T)

  test.hs:6:
      Unacceptable argument type in foreign declaration: T


On the way, I moved isFFIArgumentTy and friends out of TysWiredIn,
where they didn't really belong, into TcType.  That in turn force
me to move isStrictType, and isPrimitiveType.