Patches for DMD2 interface generation: cleanup, bugfixes and prettyprinting

[Norbert Nemec]

Hi there,

I just spent most of this weekend digging into the DMD compiler code and 
came up with a set of patches that might be of interest:

     http://d.puremagic.com/issues/show_bug.cgi?id=4713

All started out with the attempt to create .di interface files for 
phobos2. The resulting .di files were too ugly to read and even DMD 
itself refused to eat them.

Trying to fix the problem, I started digging deeper and deeper. Finally, 
the bugs were fixed, the resulting .di files are now correctly indented 
and readable and the compiler code itself has even become a bit cleaner 
and more compact.

It would be good if these patches would find their way into DMD soon. 
The bulk of the changes are trivial but quite nonlocal, so merging will 
quickly become difficult...

Greetings,
Norbert