Use "monospace" face name for all Unix systems, hopefully it should work.

Use "monospace" face name for all Unix systems, hopefully it should work.

This fixes failures of several build bot slaves (all running Debian or
Ubuntu) which were due to using "Fixed" under these Linux distributions.

Unfortunately "Fixed" didn't work as Pango doesn't seem to recognize it as a
valid face name. "DejaVu Sans" should probably work on most current Linux
systems but "Monospace" should hopefully be available on other Unix systems as
well.

We could also just take whatever wxFontEnumerator returns which should
probably be even more fool-proof.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64041 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775