Substitute hdbdir in man pages for use with --with-hdbdir

[2xsaiko]

Is your feature request related to a problem? Please describe.
When changing the database directory using --with-hdbdir, the installed man pages still refer to the original and now incorrect /var/heimdal.

Describe the solution you'd like
Have templates for the manpages into which the value of hdbdir is inserted during the build.

Describe alternatives you've considered
Manually replacing the default path with the desired path in the man pages as part of the distro package build script.

Additional context