[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

llvm-svn: 336369
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 4a8f3f994821e752319b9c76ed772ec0c40b5d03
diff --git a/include/regex b/include/regex
index 612fa84..84aacc0 100644
--- a/include/regex
+++ b/include/regex
@@ -968,7 +968,7 @@
 };
 
 template <regex_constants::error_type _Ev>
-_LIBCPP_NORETURN inline _LIBCPP_ALWAYS_INLINE
+_LIBCPP_NORETURN inline _LIBCPP_INLINE_VISIBILITY
 void __throw_regex_error()
 {
 #ifndef _LIBCPP_NO_EXCEPTIONS