winedbg: Moved into a common function all code dealing with printing information about an exception, and use this function to implement new 'info exception' command.

Truncating a large stream to less than 0x1000 bytes would cause an
unnecessarily expensive conversion.

They're just containers for their subresources.

This is the recommended way to read back render targets. It's also much faster
on current wined3d, but that's mostly a side effect of imperfections in our
resource location management.