[LCG] Add the really, *really* boring edge insertion case: adding an
edge entirely within an existing SCC. Shockingly, making the connected
component more connected is ... a total snooze fest. =]

Anyways, its wired up, and I even added a test case to make sure it
pretty much sorta works. =D

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207631 91177308-0d34-0410-b5e6-96231b3b80d8