Update SetVector to rely on the underlying set's insert to return a pair<iterator, bool>

This is to be consistent with StringSet and ultimately with the standard
library's associative container insert function.

This lead to updating SmallSet::insert to return pair<iterator, bool>,
and then to update SmallPtrSet::insert to return pair<iterator, bool>,
and then to update all the existing users of those functions...

llvm-svn: 222334
diff --git a/llvm/lib/CodeGen/SjLjEHPrepare.cpp b/llvm/lib/CodeGen/SjLjEHPrepare.cpp
index df6ba0b..7fd8107 100644
--- a/llvm/lib/CodeGen/SjLjEHPrepare.cpp
+++ b/llvm/lib/CodeGen/SjLjEHPrepare.cpp
@@ -140,7 +140,7 @@
 /// we reach blocks we've already seen.
 static void MarkBlocksLiveIn(BasicBlock *BB,
                              SmallPtrSetImpl<BasicBlock *> &LiveBBs) {
-  if (!LiveBBs.insert(BB))
+  if (!LiveBBs.insert(BB).second)
     return; // already been here.
 
   for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)