Dimitry Andric:  many visibility fixes.  Howard:  Much appreciated.  Can you send me a patch to CREDITS.TXT?

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@163862 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/bitset b/include/bitset
index 0c40b9b..1167f50 100644
--- a/include/bitset
+++ b/include/bitset
@@ -626,7 +626,7 @@
 {
 }
 
-template <size_t _Size> class bitset;
+template <size_t _Size> class _LIBCPP_VISIBLE bitset;
 template <size_t _Size> struct hash<bitset<_Size> >;
 
 template <size_t _Size>