DMD 1.028 and 2.012 releases

[Sönke Ludwig]

Great release! Now that's really a bunch of rough corners less when comparing to 
2.007/8. The const system should now be fully usable, which is really nice. 
(I'll keep my mouth shut about tail-const class references ;)

And indeed a few 'o == null' errors were just catched by the compiler :). 
Considering that most of this happened in parts of the project which were 
written by a 'D newbie' coming from a C++ background, an error message like 
"Cannot compare contents of 'null'. Use 'is' instead of '==' when comparing for 
identity." might be a good instrument to educate such users.

I'm getting some linker errors, too - but that will have to wait until tonight.