Don't use private libc++ macros.

The visibility macros just expand to the defaults, so this isn't
needed anyway.

Test: mm
Bug: http://b/34740564
Change-Id: If0ba6b412554300823219405c1e801ceec747dd0
diff --git a/liblog/event_tag_map.cpp b/liblog/event_tag_map.cpp
index 1155422..c53ea2c 100644
--- a/liblog/event_tag_map.cpp
+++ b/liblog/event_tag_map.cpp
@@ -38,10 +38,9 @@
 
 typedef std::pair<MapString, MapString> TagFmt;
 
-template <> struct _LIBCPP_TYPE_VIS_ONLY std::hash<TagFmt>
+template <> struct std::hash<TagFmt>
         : public std::unary_function<const TagFmt&, size_t> {
-    _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(const TagFmt& __t) const _NOEXCEPT {
+    size_t operator()(const TagFmt& __t) const noexcept {
         // Tag is typically unique.  Will cost us an extra 100ns for the
         // unordered_map lookup if we instead did a hash that combined
         // both of tag and fmt members, e.g.: