Cairo supports antialiasing when rendering but can be slow when set to
sub-pixel mode. This bumps the minimum version of Cairo to 1.12
(available in 14.04 LTS as well as mingw) to support three antialias
settings (fast, good, best) that offer speed/appearance tradeoffs.
This can provide a higher-quality eeschema render as it works on a
per-element basis as opposed to the OpenGL per-screen antialias.
- support for background color setting
- removed several global config settings (such as g_Drc_On)
- wrapped most of global config settings in PCB_GENERAL_SETTINGS class
- reorganized PCB general options dialog to clearly mark which options concern only the legacy canvas
- new GAL feature for legacy users: double-click (or E) to change track width available as an option.
Fixes: lp:1530543
* https://bugs.launchpad.net/kicad/+bug/1530543
Fixes: lp:1707145
* https://bugs.launchpad.net/kicad/+bug/1707145