Merge pull request #638 from chrox/master

use two finger swipe west/east to close TOC and bookmark respectively
Consider as corrupt a null-area bbox

Fixes crash with empty page_states
Merge pull request #639 from thotypous/master

Consider as corrupt a null-area bbox
Update defaults.lua

Frontlight decrease of sensitivity for two-fingered pan gesture
Update readerfrontlight.lua

Frontlight decrease of sensitivity for two-fingered pan gesture
Update readerfrontlight.lua

Frontlight decrease of sensitivity for two-fingered pan gesture
Merge pull request #641 from Markismus/master

Frontlight decrease of sensitivity for two-fingered pan gesture
refactor(doc): use ffi binding in picdocument
update koreader-base
Merge pull request #649 from houqp/houqp-master

refactor(doc): use ffi binding in picdocument
revert zip file handler to crereader
It seems that fb2.zip is a conventional format for fb2 with compression
which cannot be handled properly by mupdf.
This should fix #642.