Re-commit optimization bisect support (r267022) without new pass manager support.

The original commit was reverted because of a buildbot problem with LazyCallGraph::SCC handling (not related to the OptBisect handling).

Differential Revision: http://reviews.llvm.org/D19172

llvm-svn: 267231
diff --git a/llvm/lib/IR/LLVMContextImpl.h b/llvm/lib/IR/LLVMContextImpl.h
index 0d6d979..a4d7b7e 100644
--- a/llvm/lib/IR/LLVMContextImpl.h
+++ b/llvm/lib/IR/LLVMContextImpl.h
@@ -1133,6 +1133,10 @@
 
   /// Destroy the ConstantArrays if they are not used.
   void dropTriviallyDeadConstantArrays();
+
+  /// \brief Access the object which manages optimization bisection for failure
+  /// analysis.
+  OptBisect &getOptBisect();
 };
 
 }