Merge pull request #1309 from hwhw/master

update base: fixes for tests, libk2pdfopt without mupdf linkage
updating the screen in tap handler of readerfooter is not needed

Was a hack anyway, c.f.
https://github.com/koreader/koreader/pull/1306#discussion_r21057461

Seems to be not needed anymore. If some areas are now not refreshed
anymore, that ought to be fixed in another place.

This also gets rid of redundant screen flashes.
on finish of pan gesture when scrolling, do partial refresh

it was set to a full refresh. However, we want to behave as if in
non-scrolling mode and issue a partial refresh. That might get
updated to a full refresh if the full-refresh counter has reached
the limit - which is configurable.