[phobos] Validating email addresses

[Walter Bright]

Sean Kelly wrote:
> Does it extract the address and the full name as well?  Simply validating something as an email address isn't terribly useful. 
>
>   

Terribly useful, maybe not. But it is useful in that:

1. lots of code does email validation, and most do it wrong

2. it's a hard thing to get right

3. writing internet software is increasingly important, and supporting 
that in Phobos with quality functions is worthwhile

To me, it's like writing the math gamma function. How many programs 
would use it? Very few. But having a well done implementation is 
appreciated by those who do need it, and it's a mark of quality in the 
library.