[NFC] Rename _LIBCPP_TYPE_VIS_ONLY to _LIBCPP_TEMPLATE_VIS

The name _LIBCPP_TYPE_VIS_ONLY is no longer accurate because both
_LIBCPP_TYPE_VIS and _LIBCPP_TYPE_VIS_ONLY expand to
__attribute__((__type_visibility__)) with Clang. The only remaining difference
is that _LIBCPP_TYPE_VIS_ONLY can be applied to templates whereas
_LIBCPP_TYPE_VIS cannot (due to dllimport/dllexport not being allowed on
templates).

This patch renames _LIBCPP_TYPE_VIS_ONLY to _LIBCPP_TEMPLATE_VIS.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@291035 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/string_view b/include/string_view
index e66ac40..f98bbb5 100644
--- a/include/string_view
+++ b/include/string_view
@@ -177,7 +177,7 @@
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template<class _CharT, class _Traits = char_traits<_CharT> >
-class _LIBCPP_TYPE_VIS_ONLY basic_string_view {
+class _LIBCPP_TEMPLATE_VIS basic_string_view {
 public:
 	// types
 	typedef _Traits                                    traits_type;
@@ -735,7 +735,7 @@
 
 // [string.view.hash]
 template<class _CharT, class _Traits>
-struct _LIBCPP_TYPE_VIS_ONLY hash<basic_string_view<_CharT, _Traits> >
+struct _LIBCPP_TEMPLATE_VIS hash<basic_string_view<_CharT, _Traits> >
     : public unary_function<basic_string_view<_CharT, _Traits>, size_t>
 {
     size_t operator()(const basic_string_view<_CharT, _Traits> __val) const _NOEXCEPT;