Revert "Give internal classes hidden visibility."

It works with clang, but GCC has different rules so we can't make all of those
hidden. This reverts commit r190534.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190536 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/BranchFolding.h b/lib/CodeGen/BranchFolding.h
index 9ca0f29..0d15ed7 100644
--- a/lib/CodeGen/BranchFolding.h
+++ b/lib/CodeGen/BranchFolding.h
@@ -21,7 +21,7 @@
   class TargetInstrInfo;
   class TargetRegisterInfo;
 
-  class LLVM_LIBRARY_VISIBILITY BranchFolder {
+  class BranchFolder {
   public:
     explicit BranchFolder(bool defaultEnableTailMerge, bool CommonHoist);