libc++ locale: Disable cat*() on CloudABI. Also make tiny cleanups.

[ed]

Summary

On a new platform that I am working on (https://github.com/NuxiNL/cloudlibc) I am not implementing the cat{open,close,gets}() API, just like Android, Newlib, etc.

Instead of adding yet another operating system name to the #ifs, introduce _LIBCPP_HAS_CATOPEN in include/__config. Also adjust the code to only pull in nl_types.h when _LIBCPP_HAS_CATOPEN is set. We only needed this header for the cat*() API.

[mclow.lists]

This looks OK to me.

libcxx/trunk/include/__config

 #define _LIBCPP_NONUNIQUE_RTTI_BIT (1ULL << 63)
 #endif
 
 #if defined(__APPLE__) || defined(__FreeBSD__) || defined(_WIN32) || \
     defined(__sun__) || defined(__NetBSD__) || defined(__CloudABI__)
 #define _LIBCPP_LOCALE__L_EXTENSIONS 1
 #endif
 
+#if !defined(_WIN32) && !defined(__ANDROID__) && !defined(_NEWLIB_VERSION) && \
+    !defined(__CloudABI__)
+#define _LIBCPP_HAS_CATOPEN 1
+#endif
+
 #ifdef __FreeBSD__
 #define _DECLARE_C99_LDBL_MATH 1
 #endif
 
 #if defined(__APPLE__) || defined(__FreeBSD__)
 #define _LIBCPP_HAS_DEFAULTRUNELOCALE
 #endif
 

libcxx/trunk/include/locale

 #include <ctime>
 #if defined(_LIBCPP_MSVCRT) || defined(__MINGW32__)
 #include <support/win32/locale_win32.h>
 #elif defined(_NEWLIB_VERSION)
 // FIXME: replace all the uses of _NEWLIB_VERSION with __NEWLIB__ preceded by an
 // include of <sys/cdefs.h> once https://sourceware.org/ml/newlib-cvs/2014-q3/msg00038.html
 // has had a chance to bake for a bit
 #include <support/newlib/xlocale.h>
-#elif !defined(__ANDROID__)
+#endif
+#ifdef _LIBCPP_HAS_CATOPEN
 #include <nl_types.h>
 #endif
 
 #ifdef __APPLE__
 #include <Availability.h>
 #endif
 
 #include <__undef_min_max>

 template <class _CharT>
 locale::id
 messages<_CharT>::id;
 
 template <class _CharT>
 typename messages<_CharT>::catalog
 messages<_CharT>::do_open(const basic_string<char>& __nm, const locale&) const
 {
-#if defined(_WIN32) || defined(__ANDROID__) || defined(_NEWLIB_VERSION)
-    return -1;
-#else // _WIN32 || __ANDROID__
+#ifdef _LIBCPP_HAS_CATOPEN
     catalog __cat = (catalog)catopen(__nm.c_str(), NL_CAT_LOCALE);
     if (__cat != -1)
         __cat = static_cast<catalog>((static_cast<size_t>(__cat) >> 1));
     return __cat;
-#endif // _WIN32 || __ANDROID__
+#else // !_LIBCPP_HAS_CATOPEN
+    return -1;
+#endif // _LIBCPP_HAS_CATOPEN
 }
 
 template <class _CharT>
 typename messages<_CharT>::string_type
 messages<_CharT>::do_get(catalog __c, int __set, int __msgid,
                          const string_type& __dflt) const
 {
-#if defined(_WIN32) || defined(__ANDROID__) || defined(_NEWLIB_VERSION)
-    return __dflt;
-#else // _WIN32
+#ifdef _LIBCPP_HAS_CATOPEN
     string __ndflt;
     __narrow_to_utf8<sizeof(char_type)*__CHAR_BIT__>()(back_inserter(__ndflt),
                                                        __dflt.c_str(),
                                                        __dflt.c_str() + __dflt.size());
     if (__c != -1)
         __c <<= 1;
     nl_catd __cat = (nl_catd)__c;
     char* __n = catgets(__cat, __set, __msgid, __ndflt.c_str());
     string_type __w;
     __widen_from_utf8<sizeof(char_type)*__CHAR_BIT__>()(back_inserter(__w),
                                                         __n, __n + strlen(__n));
     return __w;
-#endif // _WIN32
+#else // !_LIBCPP_HAS_CATOPEN
+    return __dflt;
+#endif // _LIBCPP_HAS_CATOPEN
 }
 
 template <class _CharT>
 void
 messages<_CharT>::do_close(catalog __c) const
 {
-#if !defined(_WIN32) && !defined(__ANDROID__) && !defined(_NEWLIB_VERSION)
+#ifdef _LIBCPP_HAS_CATOPEN
     if (__c != -1)
         __c <<= 1;
     nl_catd __cat = (nl_catd)__c;
     catclose(__cat);
-#endif // !_WIN32
+#endif // _LIBCPP_HAS_CATOPEN
 }
 
 _LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS messages<char>)
 _LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS messages<wchar_t>)
 
 template <class _CharT>
 class _LIBCPP_TYPE_VIS_ONLY messages_byname
     : public messages<_CharT>