When applying a new cursor clipping rect, or to the previous foreground
thread when foreground changes, to notify it of the cursor clipping rect
being reset.

And make the allocation limits more explicit.

release_vbscode doesn't do anything if ref is 0.

This typically happens when resizing a D3D child window.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=54810

It is really useful to see at a glance what function is
segfaulting/crashing here when debugging games/apps.

This code is generated, and when generating WineVulkan against different
Vulkan spec versions, etc it may be misleading that the Line: referred
to by the assert dialog does not match what is generated locally on
a different machine for the same Wine version/commit.
Signed-off-by: Joshua Ashton <joshua@froggi.es>