[libc++] Make _LIBCPP_TYPE_VIS export members

Summary:
Most classes annotated with _LIBCPP_TYPE_VIS need to have at least some
of their members exported, otherwise we have a lot of link errors when
linking against a libc++ built with hidden visibility. This also makes
_LIBCPP_TYPE_VIS be consistent across platforms, since on Windows it
already exports members.

With this change made, any template methods of a class marked
_LIBCPP_TYPE_VIS will also get default visibility when instantiatied,
which is not desirable for clients of libc++ headers who wish to control
their visibility; this is the same issue as PR30642. Annotate all
problematic methods with an explicit visibility specifier to avoid this.

The problematic methods were found by running bad-visibility-finder [1]
against the libc++ headers after making the _LIBCPP_TYPE_VIS change. The
small methods were marked for inlining; the larger ones hidden.

[1] https://github.com/smeenai/bad-visibility-finder

Reviewers: mclow.lists, EricWF

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D25208

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@296732 91177308-0d34-0410-b5e6-96231b3b80d8

include/shared_mutex

@@ -220,6 +220,7 @@ public:
             return try_lock_until(chrono::steady_clock::now() + __rel_time);
         }
     template <class _Clock, class _Duration>
+        _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
         bool
         try_lock_until(const chrono::time_point<_Clock, _Duration>& __abs_time);
     void unlock();
@@ -235,6 +236,7 @@ public:
             return try_lock_shared_until(chrono::steady_clock::now() + __rel_time);
         }
     template <class _Clock, class _Duration>
+        _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
         bool
         try_lock_shared_until(const chrono::time_point<_Clock, _Duration>& __abs_time);
     void unlock_shared();