missing dejavusansmono in rrdtool pango cairo fontconfig - new insights

[macports at parvis.nl]

For a Munin 2.0.x port I encountered the problem that cairo with it quartz backend ignores the fontconfig backend that recognizes the fonts that macports installs.

Summary:
- Munin uses rrdtool, rrdtool expects DejaVuSans and DejaVuSansMono. They are both replaced by helvetica.
- For rrdtool an environment variable PANGOCAIRO_BACKEND=fc solves this.
- Munin also has a cgi interface, so in Apache config the same SetEnv is needed.

Discussion:
- In the cairo Portfilevariant +quartz is enforced, that is what is causing my problems.
- I cannot find a single need for quartz that wouldn't be provided for by fontconfig, and fontconfig is the standard for the world outside Mac.
- So I propose to change the enforced backend in cairo from quartz to fontconfig.
- port echo depends:cairo gives only 132 results ;-)