x11: round the scaled size *up* when we get a ConfigureNotify

x11: round the scaled size *up* when we get a ConfigureNotify

Although we specify a resize increment to try and get a size that is
a multiple of the window scale, maximization typically wins
over the resize increment, so the window might be odd sized.

Round *up* in this case, rather than down, since it's better to
truncate a line or two at the bottom and right of the window rather
than have a line or two that we don't know what to do with.

https://bugzilla.gnome.org/show_bug.cgi?id=739750