gdi32: CreateBitmap and friends should return stock DEFAULT_BITMAP if requested bitmap width or height is 0.

credui: Fill out the username, password and domain edit boxes from the values input to CredUIPromptForCredentialsW.

Set the focus to the password edit box, unless the user edit box is empty.

winapi_check: Print a warning when 'long' is used in an API file as this type is not Win64 compatible.

- Add error messages when unimplemented functions are called on
  non-linux platforms.
- Implement retrieving the interface list on MacOS X (and other
  platforms that use NET_RT_DUMP).

Prevents paint_count values from being skewed when hiding windows.