Documentation on DMD source

[Daniel Keep]

Unknown W. Brackets wrote:
> You'll get a lot of use out of defining the debugs for #ifdefs, and/or
> uncommenting printfs and following it.
> 
> If your code may not be running, use a breakpoint or printf to ensure it
> is.
> 
> -[Unknown]

I finally found out why my changes weren't working.

Because typinf.c is the ONE file in the frontend that doesn't get passed
$(XFLAGS) when built.  Guess where I put the -D for my changes?  Go on,
guess.  You'll never get it.

*bangs head repeatedly*

Now I have an entirely DIFFERENT problem; I officially have NO idea what
the code I modified does.  :'(

  -- Daniel