RFC: fix fcntl support in linux-user - new try

RFC: fix fcntl support in linux-user - new try

Hi,

This is a new try to fix the fcntl support in linux-user. I tried to
adress all comments but as the previous version is several weeks old,
it's possible that I've missed some.

This patch doesn't handle linux specific fcntl flags. My plan is to get
this version of the patch reviewed/fixed and then, add them if wanted.

Thanks,
Arnaud

Signed-off-by: Arnaud Patard (Rtp) <arnaud.patard@rtp-net.org>
Signed-off-by: Riku Voipio <riku.voipio@iki.fi>