The theme cursor size was ignored when setting custom cursors
such as the knife, only the DPI from GHOST was taken into account.
This meant cursors such as the knife would sometimes display too small.
Now when the theme-size is larger, a larger cursor will be used.
Currently the theme size is read from XCURSOR_SIZE environment variable
however it may be read from the system preferences in the future.
Also fix the software cursor sizes which incorrectly used the UI scale
preference which is ignored by cursor sizes.
2a757f469c