[Development] [HEADS-UP] stable branch is DEAD

[Oswald Buddenhagen]

just a small reminder that 'stable' is dead in all released qt repos and
you are supposed to push fixes to 5.3.
in fact, at this point i'd like to delete the branch. that means that
all pending changes should be reviewed, and the approved ones actually
staged (hand-hold your drive-by contributors a bit).
i'll disable the stage button on friday evening, and we'll do a last
merge to 5.3 somewhat later. afterwards the stable branch ceases to
exist.

the 5.3.1 branch will meet the same fate; i think it's already
completely forward-merged.