bug 9854: add ttf-dejavu as dependency for Debian packages

bug 9854: add ttf-dejavu as dependency for Debian packages

ttf-dejavu (i.e., the core and extra DejaVu TrueType) fonts
are used by the proposed fix for bug 8375.

To test, build and install the Koha packages for Debian
and verify that the ttf-dejavu package is installed.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Chris Nighswonger <cnighswonger@foundations.edu>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>