gpgscm: Improve parsing.

* tests/gpgscm/scheme.c (port_increment_current_line): Avoid creating
the same integer if the delta is zero.  This happens a lot during
parsing, and puts pressure on the memory allocator.

Signed-off-by: Justus Winter <justus@g10code.com>

tests/gpgscm/scheme.c

@@ -1735,6 +1735,9 @@ port_clear_location (scheme *sc, port *p)
 static void
 port_increment_current_line (scheme *sc, port *p, long delta)
 {
+  if (delta == 0)
+    return;
+
   p->curr_line =
     mk_integer(sc, ivalue_unchecked(p->curr_line) + delta);
 }