RTS option parsing

[Edward Z. Yang]

Hi David,

> I was initially thinking of something like getopt_long_only, as per:
>   http://linux.die.net/man/3/getopt_long
> however it looks like the portability of that function isn't the greatest,
> and from looking at rts/RtsFlags.c:procRtsOpts(...) it might not be the
> best solution.

That's not necessarily true; we target MingW for Windows compilation,
so if you can make sure it works there getopt_long may be viable.  On
the other hand, maintaining backwards compatibility may be tricky.
Some investigation is probably necessary.

Edward