Convert a bunch of loops to foreach.  NFC.

After r244074, we now have a successors() method to iterate over
all the successors of a TerminatorInst.  This commit changes a bunch
of eligible loops to use it.

llvm-svn: 244260
diff --git a/llvm/lib/IR/BasicBlock.cpp b/llvm/lib/IR/BasicBlock.cpp
index b5671a6..76bf176 100644
--- a/llvm/lib/IR/BasicBlock.cpp
+++ b/llvm/lib/IR/BasicBlock.cpp
@@ -404,8 +404,7 @@
     // Cope with being called on a BasicBlock that doesn't have a terminator
     // yet. Clang's CodeGenFunction::EmitReturnBlock() likes to do this.
     return;
-  for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) {
-    BasicBlock *Succ = TI->getSuccessor(i);
+  for (BasicBlock *Succ : TI->successors()) {
     // N.B. Succ might not be a complete BasicBlock, so don't assume
     // that it ends with a non-phi instruction.
     for (iterator II = Succ->begin(), IE = Succ->end(); II != IE; ++II) {