Resurrect some ancient code to add spill ranges without attempting folding,...

Resurrect some ancient code to add spill ranges without attempting folding, remat, or splitting.  This code has been updated to current APIs
in so far as it compiles and, in theory, works, but does not take advantage of recent advancements.  For instance, it could be improved by using
MachineRegisterInfo::use_iterator.

llvm-svn: 54924