[warning] end iterators dereferences in _M_extract_float and _int !!

[Paolo Carlini]

Hi,

an important warning: I have just noticed that, due to the
current structure of both _M_extract_float and _M_extract_int,
there are endemic risks of _end iterator dereferences_ !!

Systematically, we do *(++__beg) _before_ checking that, in
fact, __beg != __end !!!

My gosh!

I'm working on it, highest priority, I hope to have a fix ready
by the end of the week...

Paolo.