[TI removal] Remove `TerminatorInst` from BasicBlockUtils.h

This requires updating a number of .cpp files to adapt to the new API.
I've just systematically updated all uses of `TerminatorInst` within
these files te `Instruction` so thta I won't have to touch them again in
the future.

llvm-svn: 344498
diff --git a/llvm/lib/Transforms/Utils/LibCallsShrinkWrap.cpp b/llvm/lib/Transforms/Utils/LibCallsShrinkWrap.cpp
index 9832a6f..e1592c8 100644
--- a/llvm/lib/Transforms/Utils/LibCallsShrinkWrap.cpp
+++ b/llvm/lib/Transforms/Utils/LibCallsShrinkWrap.cpp
@@ -487,7 +487,7 @@
   MDNode *BranchWeights =
       MDBuilder(CI->getContext()).createBranchWeights(1, 2000);
 
-  TerminatorInst *NewInst =
+  Instruction *NewInst =
       SplitBlockAndInsertIfThen(Cond, CI, false, BranchWeights, DT);
   BasicBlock *CallBB = NewInst->getParent();
   CallBB->setName("cdce.call");