[LLVM-C][OCaml] Add LowerAtomic pass to C and OCaml APIs

Summary:
Adds LLVMAddLowerAtomicPass to expose createLowerAtomicPass in the C
and OCaml APIs.

Reviewers: whitequark, deadalnix

Reviewed By: whitequark

Subscribers: jfb, llvm-commits

Differential Revision: https://reviews.llvm.org/D52211

llvm-svn: 342475
diff --git a/llvm/lib/Transforms/Scalar/Scalar.cpp b/llvm/lib/Transforms/Scalar/Scalar.cpp
index 526487d..c8feedf 100644
--- a/llvm/lib/Transforms/Scalar/Scalar.cpp
+++ b/llvm/lib/Transforms/Scalar/Scalar.cpp
@@ -194,6 +194,10 @@
   unwrap(PM)->add(createLoopUnswitchPass());
 }
 
+void LLVMAddLowerAtomicPass(LLVMPassManagerRef PM) {
+  unwrap(PM)->add(createLowerAtomicPass());
+}
+
 void LLVMAddMemCpyOptPass(LLVMPassManagerRef PM) {
   unwrap(PM)->add(createMemCpyOptPass());
 }