Make locale code compile on CloudABI.

[ed]

Summary

After D10690 lands, libc++'s locale code will compile on CloudABI, with the exception of the following two bits:

• CloudABI doesn't have setlocale(), as the C library does not keep track of any global state. The global locale is always set to "C". Disable the call to setlocale() on this system.
• Similarly, mbtowc_l() is also not present, as it is also not thread-safe. As CloudABI does not support state-dependent encodings, simply disable that part of the logic.

After D10690 and this patch hit the tree, the locale code will compile out of the box on CloudABI.

[ed]

Friendly ping! :-)

[jroelofs]

LGTM

src/locale.cpp

     locale& g = __global();
     locale r = g;
     g = loc;
+#ifndef __CloudABI__
     if (g.name() != "*")
         setlocale(LC_ALL, g.name().c_str());
+#endif
     return r;
 }
 

 int
 codecvt<wchar_t, char, mbstate_t>::do_encoding() const  _NOEXCEPT
 {
+#ifndef __CloudABI__
 #ifdef _LIBCPP_LOCALE__L_EXTENSIONS
-    if (mbtowc_l(nullptr, nullptr, MB_LEN_MAX, __l) == 0)
+    if (mbtowc_l(nullptr, nullptr, MB_LEN_MAX, __l) != 0)
 #else
-    if (__mbtowc_l(nullptr, nullptr, MB_LEN_MAX, __l) == 0)
+    if (__mbtowc_l(nullptr, nullptr, MB_LEN_MAX, __l) != 0)
 #endif
-    {
-        // stateless encoding
+        return -1;
+#endif
+
+    // stateless encoding
 #ifdef _LIBCPP_LOCALE__L_EXTENSIONS
-        if (__l == 0 || MB_CUR_MAX_L(__l) == 1)  // there are no known constant length encodings
 #else
-        if (__l == 0 || __mb_cur_max_l(__l) == 1)  // there are no known constant length encodings
 #endif
-            return 1;                // which take more than 1 char to form a wchar_t
-         return 0;
-    }
-    return -1;
 }
 
 bool