LoopUnroll: Create sub-loops in LoopInfo

`LoopUnrollPass` says that it preserves `LoopInfo` -- make it so.  In
particular, tell `LoopInfo` about copies of inner loops when unrolling
the outer loop.

Conservatively, also tell `ScalarEvolution` to forget about the original
versions of these loops, since their inputs may have changed.

Fixes PR20987.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219241 91177308-0d34-0410-b5e6-96231b3b80d8
R600: Remove dead code

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219242 91177308-0d34-0410-b5e6-96231b3b80d8
[Bugpoint] Close error log in ProcessFailure. Bugpoint had been failing to close
this, and in some circumstances (e.g. reducing particularly large test-cases)
this was causing bugpoint to be killed for hitting open file-handle limits.

No test case: I was only able to trigger this with test cases taking upwards of
10 mins to run.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219244 91177308-0d34-0410-b5e6-96231b3b80d8