Fortification of STL

[Paolo Carlini]

Hi Jakub,

>The following patch of course is not meant to be directly used,
>this should only be enabled if
>1) _FORTIFY_SOURCE is defined
>2) __OPTIMIZE__ > 0
>3) we know the C library provides the checking functions (__memcpy_chk,
>   __memmove_chk, __memset_chk in this case)
>and having conditionals everywhere is jus too ugly to live with.
>Guess some __gnu_* namespace could have an __attribute__((always_inline))
>memcpy, memmove and memset routine that would either return
>__builtin_* or __builtin___*_chk depending on preprocessor macros...
>  
>
Maybe it would be just matter of adding a few forwarding macros to 
bits/c++config, similarly to what we have in ext/atomicity.h. Likewise, 
we should probably add  a bit of configury to enable the *_chk versions 
in the exported library facilities.

Paolo.