Change the way that the TD pass inlines graphs. Instead of inlining each

Change the way that the TD pass inlines graphs.  Instead of inlining each
graph into all of the functions it calls when we visit a graph, change it so
that the graph visitor inlines all of the callers of a graph into the current
graph when it visits it.

While we're at it, inline global information from the GG instead of from each
of the callers.  The GG contains a superset of the info that the callers do
anyway, and this way we only need to do it one time (not one for each caller).

This speeds up the TD pass substantially on several programs, and there is
still room for improvement.  For example, the TD pass used to take 147s
on perlbmk, it now takes 36s.  On povray, we went from about 5s to 1.97s.
134.perl is down from ~1s for Loc+BU+TD to .6s.

The TD pass needs a lot of improvement though, which will occur with later
patches.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@20723 91177308-0d34-0410-b5e6-96231b3b80d8