ttf-dejavu-core is a transitional package in sid, depend on fonts-dejavu-core
Set debian/compat to 9
Update the Standards-Version field to 3.9.4
Add dependency on www-browser for cppreference-doc-en-html
The priority of the package is 'optional', not 'extra'
Add postinst and postrm scripts to register the qch file in the QT assistant
Reword the description message to fit in 80 characters
Do not distribute fonts that came with the upstream tarball