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/regex

@@ -968,7 +968,7 @@ public:
 };
 
 template <regex_constants::error_type _Ev>
-_LIBCPP_NORETURN inline _LIBCPP_INLINE_VISIBILITY
+_LIBCPP_NORETURN inline _LIBCPP_ALWAYS_INLINE
 void __throw_regex_error()
 {
 #ifndef _LIBCPP_NO_EXCEPTIONS