[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.

llvm-svn: 291035
diff --git a/libcxx/include/set b/libcxx/include/set
index 8e4c2ae..be5c952 100644
--- a/libcxx/include/set
+++ b/libcxx/include/set
@@ -397,7 +397,7 @@
 
 template <class _Key, class _Compare = less<_Key>,
           class _Allocator = allocator<_Key> >
-class _LIBCPP_TYPE_VIS_ONLY set
+class _LIBCPP_TEMPLATE_VIS set
 {
 public:
     // types:
@@ -810,7 +810,7 @@
 
 template <class _Key, class _Compare = less<_Key>,
           class _Allocator = allocator<_Key> >
-class _LIBCPP_TYPE_VIS_ONLY multiset
+class _LIBCPP_TEMPLATE_VIS multiset
 {
 public:
     // types: