dpkg: Mark the summarize_filename() ellipsed string for translation

Coallesce the ellipsed string with the format string so that it makes a
bit more sense for translators. This will allow translators to use for
example the UTF-8 ellipsis character.

src/processarc.c

@@ -71,8 +71,7 @@ summarize_filename(const char *filename)
 
   if (pfilename && pfilename != filename) {
     pfilenamebuf = nfmalloc(strlen(pfilename) + 5);
-    strcpy(pfilenamebuf, ".../");
-    strcat(pfilenamebuf, pfilename);
+    sprintf(pfilenamebuf, _(".../%s"), pfilename);
     pfilename = pfilenamebuf;
   } else {
     pfilename = filename;