Bug 694753: Android: Recompute the patch on PageView.update()

In some cases freshly-created annotations could fail to appear because the HQ patch was
being left in place even when zoomed fully in, and when in that state, the patch was not
updated. The bug was usually hidden by an onLayout call being triggered with an out-
of-date patch, which causes the HQ patch to be removed. The bug is fixed by having
addHq remove the patch when fully zoomed out. Since now addHq may sometimes add
the patch and sometimes remove it, I've renamed it to updateHq.

Correctness of this fix has not been checked because I was unable to trigger the bad
behaviour on my test device.
Bug 694729: Rounding the Ink

Use round caps and joins so as to better match the result of drawing, and also
so that single dots display. Thanks to Michael Cadilhac for the suggestion.
Bug 694732: Android: draw single point strokes when inking

Make single-point strokes display by special casing them as
circles. Thanks for Michael Cadilhac for the suggestion.
Bug 694569: suspicious for loop in pdf-device.c

Replace an explicit i = i by a comment in a for loop where i is
already at the correct starting value.