[phobos] Can someone please fix isemail for Linux64?

[Jonathan M Davis]

> I don't think this ever compiled successfully on 64 bits (when it was
> originally committed, the failure was masked by compiler bugs).
> 
> std/net/isemail.d(375): Error: cannot implicitly convert expression
> (lastIndexOf(addressLiteral,front(matchesIp),cast(CaseSensitive)1)) of
> type long to int
> make[1]: *** [generated/linux/debug/64/unittest/std/net/isemail] Error 1

Done. It's one of those cases where size_t should have been used but wasn't. 
It's actually one of those few cases where auto is a bad idea, because the 
initial index ended up being an int.

- Jonathan M Davis