Incremental compilation with DMD

[Walter Bright]

Tom S wrote:
> Personally I'm of the opinion that functions should 
> be explicitly marked for CTFE, and this is just another reason for such. 
> I'm using a patched DMD with added pragma(ctfe) which instructs the 
> compiler not to run any codegen or generate debug info 
> functions/aggregates marked as such. This trick alone can slim an 
> executable down by a good megabyte, which sometimes is a life-saver with 
> OPTLINK.

If you are compiling files with -lib, and nobody calls those CTFE 
functions at runtime, then they should never be linked in. (Virtual 
functions are always linked in, as they have a reference to them even if 
they are never called.)

Executables built this way shouldn't have dead functions in them.