Update font-kit to v0.14 and freetype-sys to v0.20

plotters-bitmap's autopkgtests have been failing since July due to a font-kit bug which mainly affects plotters. plotters' examples would show this, but they are disabled for unrelated reasons. Updating plotters' font-kit dep to v0.14 fixes the bug. It requires bumping freetype-sys to v0.20 and touching a few rdeps. Do not attempt updating font-kit to v0.12 as it would cause SIGSEGVs in the tests.