Pass flags to Clang about documentalist

[mxswd]

In terms of command line options, you would want to set source parser, comment parser and writer.
We could do a -- separator. i.e. documentalist -objc -tomdoc -html-fancy -- -Obj-C --clang-option -Oh
Also lets use https://github.com/pcapriotti/optparse-applicative

[jspahrsummers]

@maxpow4h Is that better than System.Console.GetOpt in some way?

[mxswd]

Nah, we would be adding unnecessary dependencies.
It's just nice for --help and optional arguments.