py3: use integer division in curseschunkselector.printstring()
This fixes a crash when scrolling in curses UI when refresh() is called
when a float value (namely 'self.firstlineofpadtoprint', taking its
value indirectly from 'self.linesprintedtopadsofar').
crecord: drop duplicated set of firstlineofpadtoprint attribute
The attribute is already set a couple of lines above, in
curseschunkselector.__init__().