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

llvm-svn: 163862
diff --git a/libcxx/include/exception b/libcxx/include/exception
index 2f527d9..5b75fb0 100644
--- a/libcxx/include/exception
+++ b/libcxx/include/exception
@@ -116,7 +116,7 @@
 
 _LIBCPP_VISIBLE bool uncaught_exception() _NOEXCEPT;
 
-class exception_ptr;
+class _LIBCPP_VISIBLE exception_ptr;
 
 exception_ptr current_exception() _NOEXCEPT;
 _LIBCPP_NORETURN void rethrow_exception(exception_ptr);