to match the package name

add a few missing libraries and a note for the need of $FONTCONFIG_FILE

other sections are supposed to use this macros and define a part. Having
a default here is useless and maybe confusing

This reverts commit 80673c8c.

All testnodes should have been updated by now, so this commit is no
longer needed.

/reviewed-on nexedi/slapos!419

/reviewed-on nexedi/slapos!416