Rather than having a different custom legalization

hook for each way in which a result type can be
legalized (promotion, expansion, softening etc),
just use one: ReplaceNodeResults, which returns
a node with exactly the same result types as the
node passed to it, but presumably with a bunch of
custom code behind the scenes.  No change if the
new LegalizeTypes infrastructure is not turned on.

llvm-svn: 53137