Do not include manpages when installing docbooks
Review Request #128531 - Created July 26, 2016 and submitted
Remove man-*.docbook files from the list of files which are considered as dependency for the manual and which are installed. Manpages sources must be handled with kdoctools_create_manpage anyway, the installed source docbook files for them were useless.
Tested with repositories which provides docbook for manpages and regular manuals (kate, kde-baseapps/frameworks).