Revert "[libc++] Replace uses of _LIBCPP_ALWAYS_INLINE by _LIBCPP_INLINE_VISIBILITY"

This reverts commit r336369. The commit had two problems:
1. __pbump was marked as _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY instead of
   _LIBCPP_INLINE_VISIBILITY, which lead to two symbols being added in the
   dylib and the check-cxx-abilist failing.

2. The LLDB tests started failing because they undefine
   `_LIBCPP_INLINE_VISIBILITY`. I need to figure out why they do that and
   fix the tests before we can go forward with this change.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@336382 91177308-0d34-0410-b5e6-96231b3b80d8

include/experimental/filesystem

@@ -470,23 +470,23 @@ public:
     file_status& operator=(file_status&&) _NOEXCEPT = default;
 
     // observers
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_ALWAYS_INLINE
     file_type type() const _NOEXCEPT {
         return __ft_;
     }
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_ALWAYS_INLINE
     perms permissions() const _NOEXCEPT {
         return __prms_;
     }
 
     // modifiers
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_ALWAYS_INLINE
     void type(file_type __ft) _NOEXCEPT {
         __ft_ = __ft;
     }
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_ALWAYS_INLINE
     void permissions(perms __p) _NOEXCEPT {
         __prms_ = __p;
     }
@@ -1106,7 +1106,7 @@ private:
     string_type __pn_;
 };
 
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_ALWAYS_INLINE
 void swap(path& __lhs, path& __rhs) _NOEXCEPT {
     __lhs.swap(__rhs);
 }
@@ -1298,7 +1298,7 @@ private:
 };
 
 template <class... _Args>
-_LIBCPP_NORETURN inline _LIBCPP_INLINE_VISIBILITY
+_LIBCPP_NORETURN inline _LIBCPP_ALWAYS_INLINE
 #ifndef _LIBCPP_NO_EXCEPTIONS
 void __throw_filesystem_error(_Args && ...__args)
 {