move userlib to pywikibot.compat, bugfix for interwiki.py

compat folder contains compatibility libraries from compat like
query and catlib.userlib is part of page.py and this deprecated
library should also placed here.

Change-Id: If697c3e294e3e69fb7224db76742906908cdb7a2
Merge "move userlib to pywikibot.compat, bugfix for interwiki.py"