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/AllocationOrder.h b/lib/CodeGen/AllocationOrder.h
index f0d35be..aed461a 100644
--- a/lib/CodeGen/AllocationOrder.h
+++ b/lib/CodeGen/AllocationOrder.h
@@ -25,7 +25,7 @@
 class RegisterClassInfo;
 class VirtRegMap;
 
-class LLVM_LIBRARY_VISIBILITY AllocationOrder {
+class AllocationOrder {
   SmallVector<MCPhysReg, 16> Hints;
   ArrayRef<MCPhysReg> Order;
   int Pos;