[libc++] Take 2: 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.

Note that this commit had originally been applied in r336369 and then
reverted in r336382 because of unforeseen problems. Both of these problems
have now been fixed.

Reviewers: EricWF, mclow.lists

Subscribers: christof, dexonsmith, erikvanderpoel

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

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@336866 91177308-0d34-0410-b5e6-96231b3b80d8

include/__config

diff --git a/include/__config b/include/__config
index 52c7142..233c2b3 100644
--- a/include/__config
+++ b/include/__config
@@ -672,11 +672,9 @@
 
 #if defined(_LIBCPP_COMPILER_MSVC)
 #  define _LIBCPP_INLINE_VISIBILITY __forceinline
-#  define _LIBCPP_ALWAYS_INLINE     __forceinline
 #  define _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY __forceinline
 #else
 #  define _LIBCPP_INLINE_VISIBILITY __attribute__ ((__always_inline__))
-#  define _LIBCPP_ALWAYS_INLINE     __attribute__ ((__always_inline__))
 #  define _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY __attribute__ ((__always_inline__))
 #endif
 
@@ -771,14 +769,6 @@
 #  endif
 #endif
 
-#ifndef _LIBCPP_ALWAYS_INLINE
-#  if !defined(_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS)
-#    define _LIBCPP_ALWAYS_INLINE  __attribute__ ((__visibility__("hidden"), __always_inline__))
-#  else
-#    define _LIBCPP_ALWAYS_INLINE  __attribute__ ((__always_inline__))
-#  endif
-#endif
-
 #ifndef _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
 #  if !defined(_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS)
 #    define _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY __attribute__((__visibility__("default"), __always_inline__))
@@ -889,9 +879,9 @@
 #  define _LIBCPP_DECLARE_STRONG_ENUM(x) struct _LIBCPP_TYPE_VIS x { enum __lx
 #  define _LIBCPP_DECLARE_STRONG_ENUM_EPILOG(x) \
      __lx __v_; \
-     _LIBCPP_ALWAYS_INLINE x(__lx __v) : __v_(__v) {} \
-     _LIBCPP_ALWAYS_INLINE explicit x(int __v) : __v_(static_cast<__lx>(__v)) {} \
-     _LIBCPP_ALWAYS_INLINE operator int() const {return __v_;} \
+     _LIBCPP_INLINE_VISIBILITY x(__lx __v) : __v_(__v) {} \
+     _LIBCPP_INLINE_VISIBILITY explicit x(int __v) : __v_(static_cast<__lx>(__v)) {} \
+     _LIBCPP_INLINE_VISIBILITY operator int() const {return __v_;} \
      };
 #else  // _LIBCPP_HAS_NO_STRONG_ENUMS
 #  define _LIBCPP_DECLARE_STRONG_ENUM(x) enum class _LIBCPP_ENUM_VIS x