Log Message:
fonts/fontconfig: Bump bl3 API_dEPENDS to 2.11.91

If the base fontconfig is old, and some but not all fontconfig-using
packages need newer, we end up with some binaries having two different
fontconfigs.  Adjust fontconfig's API_DEPENDS to 2.11.91, because
pango needs at least that.  This means that pkgsrc fontconfig will
always be used on netbsd-8.

The only sound approach appears to be a hard choice of system vs
pkgsrc fontconfig, without per-package overrides, but that's a bigger
step.  We could also consider changing API_DEPENDS to match the pkgsrc
fontconfig, so base is only used if newer.

(Needs a revbump.)

As discussed on tech-pkg.