Description of Problem:

When starting up a second X server (startx -- :1) 
there is corruption on the screen depending on what applications are
being run. The corruption can usually seen as black areas 
in applications (screenshot attached), and can be seen in a default
GNOME/KDE desktop almost instantly. TWM + creating a few windows
and moving them around also shows similar problems. It used to work (tm), my
guess is that hardware acceleration of Xrender only works fine for
a single-head (and single server) configuration, the driver disables
acceleration if you have a dual head config.

The combination of magic Xaa options that remove the corruption seem to be

(**) MGA(0): Option "XaaNoSolidFillRect"
(**) MGA(0): Option "XaaNoSolidFillTrap"
(**) MGA(0): Option "XaaNoSolidTwoPointLine"
(**) MGA(0): Option "XaaNoScreenToScreenColorExpandFill"

(couldn't get any visible corruption after these were in use although 
there might be a few cases these don't cover). Not worth disabling
by default, I suppose, but maybe some smart workaround can be devised.
X probably isn't smart enough to know if another instance is running,
so this may not be possible...

Version-Release number of selected component (if applicable):

4.2.0-67.6

How Reproducible:

Steps to Reproduce:
1. startx 
2. startx -- :1
3. 

Actual Results:

Screen corruption on second X server

Expected Results:

Both X servers are fine