a few cleanups & fixes to the epjitsu backend
This merge request has a few cleanups & fixes for the epjitsu driver:
- it introduces the MAX() & MIN() functions to allow easier understanding of the code
- it fixes a typo
- adds DBG() instrumentation to some functions / fixes it
- makes sure that some ..._range.max values are larger than their ....range.min counterparts
- fixes an issue with ADF scanners where the page width was ignored
Please consider merging them into master
Thanks in advance Peter