rdmd: Add --extra-file option

This option includes an extra source or object in the compilation. It is
particularly useful if you need to add an extra object (compiled by
another language maybe) or an extra source (maybe because a .di was
provided) when compiling the program (multiple --extra-file are
allowed).
On Fri, Nov 07, 2014 at 05:11:01AM -0800, Vladimir Panteleev wrote:
> > @@ -661,6 +667,9 @@ private string[string] getDependencies(string rootModule, string workDir,
> >              default: assert(0);
> >              }
> >          }
> > +        // All all dependencies specified through --extra-file
> 
> Typo ("All all")

Fixed.