winex11drv: Distinguish left and right keys for shift, ctrl and alt. (try 4)

[Vitaliy Margolen]

Vitaliy Margolen wrote:
> This time with lots of tests that exposed number of other problems that 
> were fixed.
> 
> I could not separate this patch into separate pieces - they all linked 
> together and
> fixing one problem meant fixing or breaking something else. This 
> especially related
> to the tests that test everything together as a one black box.
> 
> There are still few problems remain that could be exposed by tightening 
> tests.
> ---

Anything wrong with this patch?
Vitaliy