GDB Improved D support

[Iain Buclaw]

Here's the patch against GDB for anyone who wants to review.
https://github.com/ibuclaw/gdb/commit/6c187f7250c21a1b3ba2a09942b52ad238397d43

If no one sees anything that seems wrong, I'll submit this to GDB 
this afternoon for inclusion.

Regards
Iain.