update koreader-base
Merge pull request #178 from chrox/update_crengine

update koreader-base
fix libpng conflict in libk2pdfopt
fix nil pos bug in readerhighlight
Merge pull request #182 from chrox/master

fix nil pos bug in readerhighlight
update koreader-base
Merge pull request #184 from houqp/houqp-master

update koreader-base
only set two pages mode for crengine in kindle dxg
Merge pull request #186 from houqp/houqp-master

only set two pages mode for crengine in kindle dxg
fix fractional pix returned by scaleByDPI
add vertically scrollable text widget
fix long definition not shown properly in dictionary window
Merge pull request #187 from chrox/scroll_text

fix long definition not shown properly in dictionary window
add missing scrollbar widget
Merge pull request #188 from chrox/scroll_text

add missing scrollbar widget
add keyboard widget test in wtest
add on-screen keyboard widget
update keyboard widget test in wtest
add goto page menu entry for pdfreader
fix fractional pixel coordinates in paintTo function