Add count parameter to *_{in,de}crease()

This allows for moving more than one item up/down.

This currently isn't used anywhere but will be bound to a key with one
of the following patches.

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

src/apoint.c

@@ -103,15 +103,15 @@ apoint_hilt_set (int highlighted)
 }
 
 void
-apoint_hilt_decrease (void)
+apoint_hilt_decrease (int n)
 {
-  hilt--;
+  hilt -= n;
 }
 
 void
-apoint_hilt_increase (void)
+apoint_hilt_increase (int n)
 {
-  hilt++;
+  hilt += n;
 }
 
 /* Return which appointment is highlighted. */