Lots of improvements to the new dagisel emitter. This gets it to

the point where it is to the 95% feature complete mark, it just
needs result updating to be done (then testing, optimization 
etc).

More specificallly, this adds support for chain and flag handling
on the result nodes, support for sdnodexforms, support for variadic
nodes, memrefs, pinned physreg inputs, and probably lots of other
stuff.

In the old DAGISelEmitter, this deletes the dead code related to
OperatorMap, cleans up a variety of dead stuff handling "implicit
remapping" from things like globaladdr -> targetglobaladdr (which
is no longer used because globaladdr always needs to be legalized),
and some minor formatting fixes.

llvm-svn: 96716