[libc++] Replace uses of _LIBCPP_ALWAYS_INLINE by _LIBCPP_INLINE_VISIBILITY

Summary:
We never actually mean to always inline a function -- all the uses of
the macro I could find are actually attempts to control the visibility
of symbols. This is better described by _LIBCPP_INLINE_VISIBILITY, which
is actually always defined the same.

This change is orthogonal to the decision of what we're actually going
to do with _LIBCPP_INLINE_VISIBILITY -- it just simplifies things by
having one canonical way of doing things.

Reviewers: EricWF

Subscribers: christof, llvm-commits, dexonsmith, erikvanderpoel, mclow.lists

Differential Revision: https://reviews.llvm.org/D48892

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@336369 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/experimental/filesystem b/include/experimental/filesystem
index f29e23e..1ca1796 100644
--- a/include/experimental/filesystem
+++ b/include/experimental/filesystem
@@ -470,23 +470,23 @@
     file_status& operator=(file_status&&) _NOEXCEPT = default;
 
     // observers
-    _LIBCPP_ALWAYS_INLINE
+    _LIBCPP_INLINE_VISIBILITY
     file_type type() const _NOEXCEPT {
         return __ft_;
     }
 
-    _LIBCPP_ALWAYS_INLINE
+    _LIBCPP_INLINE_VISIBILITY
     perms permissions() const _NOEXCEPT {
         return __prms_;
     }
 
     // modifiers
-    _LIBCPP_ALWAYS_INLINE
+    _LIBCPP_INLINE_VISIBILITY
     void type(file_type __ft) _NOEXCEPT {
         __ft_ = __ft;
     }
 
-    _LIBCPP_ALWAYS_INLINE
+    _LIBCPP_INLINE_VISIBILITY
     void permissions(perms __p) _NOEXCEPT {
         __prms_ = __p;
     }
@@ -1106,7 +1106,7 @@
     string_type __pn_;
 };
 
-inline _LIBCPP_ALWAYS_INLINE
+inline _LIBCPP_INLINE_VISIBILITY
 void swap(path& __lhs, path& __rhs) _NOEXCEPT {
     __lhs.swap(__rhs);
 }
@@ -1298,7 +1298,7 @@
 };
 
 template <class... _Args>
-_LIBCPP_NORETURN inline _LIBCPP_ALWAYS_INLINE
+_LIBCPP_NORETURN inline _LIBCPP_INLINE_VISIBILITY
 #ifndef _LIBCPP_NO_EXCEPTIONS
 void __throw_filesystem_error(_Args && ...__args)
 {