patch for error handling after driver callback calls.

[Alexandre Julliard]

Dave_Belanger at cimmetry.com writes:

> (See attached file: patch_callbacks_return.txt)

The idea is that the DC interface functions should behave just like
the corresponding APIs, so if the API returns the old value the DC
function should do that too. This way it guarantees that we can
implement the full behavior of the API in the driver.

-- 
Alexandre Julliard
julliard at winehq.com