Add a const version of findNearestCommonDominator to PostDom for convenience.

PR16283.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@183629 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/PostDominators.h

@@ -74,6 +74,11 @@ struct PostDominatorTree : public FunctionPass {
     return DT->findNearestCommonDominator(A, B);
   }
 
+  inline const BasicBlock *findNearestCommonDominator(const BasicBlock *A,
+                                                      const BasicBlock *B) {
+    return DT->findNearestCommonDominator(A, B);
+  }
+
   virtual void releaseMemory() {
     DT->releaseMemory();
   }