[m-rev.] for review: Remove documentation for --cross-compiling option.

[Julien Fischer]

On Wed, 25 Mar 2015, Peter Wang wrote:

> Remove documentation for --cross-compiling option.
>
> README.Linux:
> README.MacOS:
> README.MinGW-cross:
> compiler/options.m:
> 	Remove or comment out references to the `--cross-compiling'
> 	option which has no effect now.

That looks fine.

Cheers,
Julien.