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

[Marc Glisse]

On Thu, 15 Sep 2016, Felipe Magno de Almeida wrote:

+               || sizeof(uint32_t) == sizeof(void*)
+                || sizeof(uint16_t) == sizeof(void*),

Indentation is off?

> Call _M_extract_* functions family through temporary int objects

Would it make sense to use a template type instead of int for this 
parameter? Or possibly have a typedef that defaults to int (what POSIX 
requires). The hard case would be a libc that uses bitfields for the 
fields of struct tm (that could save some space), but I don't think anyone 
does that.

> float pointing

floating point?

A ChangeLog entry would also help.

-- 
Marc Glisse