Performance improvements for D / DMD compiler.

[janderson]

Dave wrote:
> 
> What's on your wish-list (let's leave the GC and other library 
> functionality out of this for now <g>)?
> 
> Here's mine:
>   - Better floating point code generation
>   - Put the tail-recursion optimization back in
>   - Omit frame pointers w/ -O switch
>   - Improved in-lining (don't arbitrarily exclude functions w/ inout 
> parameters and loops).
>   - Auto-finalization.

The above and:

- Better GC that uses meta data to only track pointers (rather then any 
number within a specific range).

- Improved efficient library functions (perhaps tango will fix this).

-Joel