[Outliner] Fixed Asan bot failure in r296418

Fixed the asan bot failure which led to the last commit of the outliner being reverted.
The change is in lib/CodeGen/MachineOutliner.cpp in the SuffixTree's constructor. LeafVector
is no longer initialized using reserve but just a standard constructor.

llvm-svn: 297081
diff --git a/llvm/lib/CodeGen/CodeGen.cpp b/llvm/lib/CodeGen/CodeGen.cpp
index b70c2b0..3ecf298 100644
--- a/llvm/lib/CodeGen/CodeGen.cpp
+++ b/llvm/lib/CodeGen/CodeGen.cpp
@@ -58,6 +58,7 @@
   initializeMachineLoopInfoPass(Registry);
   initializeMachineModuleInfoPass(Registry);
   initializeMachineOptimizationRemarkEmitterPassPass(Registry);
+  initializeMachineOutlinerPass(Registry);
   initializeMachinePipelinerPass(Registry);
   initializeMachinePostDominatorTreePass(Registry);
   initializeMachineRegionInfoPassPass(Registry);