app: Don't add extra margins by default
app: Don't add extra margins by default

This is only useful to test that VteTerminal handles all offsets
correctly, but not for normal operation. So make it a cmdline option.

thestinger/vte-ng,saitoha/vte-sixel,thestinger/vte-ng,thestinger/vte-ng,saitoha/vte-sixel,saitoha/vte-sixel