debug: Group debug messages by timestamps
debug: Group debug messages by timestamps

Instead of showing the full timestamp for debugging messages that happen
within a second, showing the delta from the previous full timestamp can
be more useful when debugging; this allows immediately seeing the time
difference, instead of doing the math in our heads.

Distrotech/clutter,Distrotech/clutter,djdeath/clutter,ebassi/clutter,jigpu/clutter,GNOME/clutter,djdeath/clutter,heysion/clutter-clone,heysion/clutter-clone,djdeath/clutter,jigpu/clutter,GNOME/clutter,djdeath/clutter-android,djdeath/clutter-android,GNOME/clutter,djdeath/clutter,jigpu/clutter,GNOME/clutter,Distrotech/clutter,Distrotech/clutter,collects/clutter,collects/clutter,ebassi/clutter,Distrotech/clutter,ebassi/clutter,Distrotech/clutter,heysion/clutter-clone,jigpu/clutter,jigpu/clutter,djdeath/clutter,heysion/clutter-clone,ebassi/clutter,jigpu/clutter,ebassi/clutter,djdeath/clutter-android,heysion/clutter-clone,djdeath/clutter,collects/clutter,collects/clutter,GNOME/clutter,collects/clutter,djdeath/clutter-android,djdeath/clutter-android