Add compact panels support

Add a configuration option that allows for switching to compact panel
mode. In this mode, all window labels are hidden, so that there's more
space for actual information.

This patch doesn't add a configuration menu entry and doesn't add any
documentation.

Implements FR#7.

Signed-off-by: Lukas Fleischer <calcurse@cryptocrack.de>

src/config.c

@@ -86,6 +86,7 @@ static int config_serialize_input_datefmt(char *, void *);
 static const struct confvar confmap[] = {
   {"appearance.calendarview", config_parse_calendar_view,
    config_serialize_calendar_view, NULL},
+  {"appearance.compactpanels", CONFIG_HANDLER_BOOL(conf.compact_panels)},
   {"appearance.defaultpanel", config_parse_default_panel,
    config_serialize_default_panel, NULL},
   {"appearance.layout", config_parse_layout, config_serialize_layout, NULL},