NT4 fails with ERROR_INVALID_TARGET_HANDLE instead of
ERROR_REDIR_PAUSED.
Use some correct messages on error.
Extra tracing.

within the visible region, clipped to the clipping region if that
exists. Add the destination of pixels coming from the outside of this
region to the update region. With tests that depend on this.

assumes screen coordinates.

all link_window is used for at this point.
Get rid of the WIN_LinkWindow/UnlinkWindow functions.

Minor cleanups.

supposed to use to draw into.

Move testing comments in a more appropriate place.

available.

defined strdupAtoW.

the installs.

forced to use US locale for string->Decimal conversion, to agree with
sprintfW().

Made WIN_GetPtr return WND_DESKTOP in that case.

conversion and the detection of the default font's codepage.

- better use of critical section
- some cleanup to better understand code paths
- logic correction on SetWindowsHookExA/UnhookWindowsHookEx on
  keyboard.