selection: fix multiline backscroll selection
selection: fix multiline backscroll selection

If the 2nd selected line has a width of 4 but the cursor was at pos 6 on
the 1st line, this line would get lost.

bssb/terminology,ihorlaitan/terminology,bssb/terminology,bssb/terminology,ihorlaitan/terminology,ihorlaitan/terminology,godfath3r/terminology,godfath3r/terminology,godfath3r/terminology