Sink the include stack printing into the generic text diagnostic

utility. This is a particularly nice win because it removes a pile of
parameters from these routines. Also name them a bit better. I'm trying
to follow the pattern of 'emit' routines writing directly to what is
expected to be the final output, while 'print' routines take a output
stream argument and can be used to build up intermediate buffers, etc.

Also, fix a bug I spotted by inspection from my last commit where
'LastLoc' and 'LastNonNoteLoc' were reversed. It's really scary that
this didn't trigger a single test failure. Will be working on tests for
more of this functionality now.

llvm-svn: 142069