s3:smbd: Add a "hidden" parameter "share:fake_fscaps"

s3:smbd: Add a "hidden" parameter "share:fake_fscaps"

This is needed to support some special app I've just come across where I had to
set the SPARSE_FILES bit (0x40) to make it work against Samba at all. There
might be others to fake. This is definitely a "Don't touch if you don't know
what you're doing" thing, so I decided to make this an undocumented parametric
parameter.

I know this sucks, so feel free to beat me up on this. But I don't think it
will hurt.