st/xorg, vmware: Make throttling configurable.

st/xorg, vmware: Make throttling configurable.

The xorg state tracker gets two new options to let the user choose
whether to enable / disable dirty throttling and swapbuffer throttling.
The default value of these options are enabled, unless the winsys
supplies a customizer with other values. The customizer record has been
extended to allow this, and also to set winsys-based throttling on a per-
context basis.

The vmware part of this patch disables the dirty throttling if the kernel
supports command submission throttling, and also in that case sets kernel
based throttling for everything but swapbuffers. The vmware winsys does not
set throttling per context, even if it theoretically could, but instead
sets throttling per screen. This should perhaps be changed, should the
xorg state tracker start to use multiple rendering contexts. Kernel throttling
is off by default for all new screens/contexts, so the dri state tracker
is not affected.

This significantly improves interactivity of the vmware xorg driver.

Cherry-picked from commit a8f3b3f88acc1f0193fa740e76e9d815f07f32ab

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Jakob Bornecrantz <jakob@vmware.com>