build: Enable maintainer mode

This adds the "rebuild rules" that ensure configure / Makefile.in gets
rebuilt when the source configure.ac / Makefile.am changes.
keyring: Remove an unused variable
timezone: Rerun gdbus-codegen when Makefile.am changes
timezone: Plug a css provider leak
timezone: Sync cc-timezone-map size allocation code with control center

This ensures the map image doesn't get scaled and blurry.
timezone: Make sure the location marker is drawn pixel-aligned
3.11.92