r.out.mpeg fails because the output file name is empty

This fix copies the output file name to the correct variable, as in GRASS 6

raster/r.out.mpeg/main.c

@@ -6,6 +6,8 @@
  *               Brad Douglas <rez touchofmadness.com>, Markus Neteler <neteler itc.it>,
  *               Glynn Clements <glynn gclements.plus.com>, Hamish Bowman <hamish_b yahoo.com>,
  *               Jan-Oliver Wagner <jan intevation.de>, Paul Kelly <paul-grass stjohnspoint.co.uk>
+ *               Paolo Zatelli <paolo.zatelli unitn.it>
+ *
  * PURPOSE:      combines a series of GRASS raster maps into a single MPEG-1
  * COPYRIGHT:    (C) 1999-2006, 2011 by the GRASS Development Team
  *
@@ -142,6 +144,9 @@ int main(int argc, char **argv)
 
     parse_command(viewopts, vfiles, &numviews, &frames);
 
+    /* output file */
+    strcpy(outfile, out->answer);
+
     r_out = 0;
     if (conv->answer)
 	r_out = 1;