Showing unittest in documentation (Was Re: std.unittests [updated] for review)

[Andrej Mitrovic]

It's often the case that you want documentation examples to be short,
but also correct. But you still want to write complex unittests that
you don't want to put in the documentation. Sounds like a perfect
candidate for named unittests:

unittest(ddoc)
{
   // outputted in documentation
}

Here "ddoc" would be a predefined identifier, kind of like X86 is for
version() statements.

unittest // our own complex unittest that we don't want to output in
the documentation
{
    // ...
}