Fix compilation errors with libstdc++v3 for AVR target and allow --enable-libstdcxx

[Jonathan Wakely]

On 10/11/16 13:51 -0200, Felipe Magno de Almeida wrote:
>--- a/libstdc++-v3/include/bits/locale_facets_nonio.tcc
>+++ b/libstdc++-v3/include/bits/locale_facets_nonio.tcc
>@@ -659,30 +659,38 @@ _GLIBCXX_END_NAMESPACE_LDBL_OR_CXX11
> 		  // Abbreviated weekday name [tm_wday]
> 		  const char_type*  __days1[7];
> 		  __tp._M_days_abbreviated(__days1);
>-		  __beg = _M_extract_name(__beg, __end, __tm->tm_wday, __days1,
>+                  __tm->tm_wday = __mem;
>+		  __beg = _M_extract_name(__beg, __end, __mem, __days1,
> 					  7, __io, __tmperr);
>+                  __mem = __tm->tm_wday;
> 		  break;

Isn't this backwards?

You assign a garbage value to tm_wday, read into __mem, then assign
the garbage back to it.

Has this change been tested?