unittests are really part of the build, not a special run

[Kapps via Digitalmars-d]

Would this change result in just not running main and changing 
the default unittest runner output, but still run static 
constructors (which then allows you to specify a custom unittest 
runner)? If so, I think it's a nice change. I've always found it 
quite odd that running unittests still runs the main method, and 
it results in annoyances when making custom build systems that 
may or may not need -main depending on if they're a library or an 
application. Having unittests not care whether main is present or 
not, and not run main, would be a nice change for tooling.