Updated gdmd/gdc man pages

[Anders F Björklund]

Johan Granberg wrote:

>>I did include the -I flag, only because -I and -J
>>are very similar and thus potentially confusing...
>>(one might want to include some other common options,
>>like for instance the usual GCC -c, -o or -g  flags?)
> 
> I think this would be a good idea. If we added the most common options and
> equivalents to dmds options where available it would be an improvement.

I don't think the DMD equivalents are all that intriguing
(if interested, one can always use "gdmd -vdmd" command),
but adding the most common options might be a good idea.

I also ignored all those options to gdmd that are simply
passed onwards to gdc, like -arch or -framework and such.
(in addition to all those usual -m... and -f... options)

And I guess GCC coverage / profiling could be mentioned
briefly in a section beneath the usual GDC options...
(list the common options, and reference gcov/gprof ?)

Perhaps mentioning the assembler and debugger, as well.

--anders