wmget: Fix resource leaks.

In particular, fclose() all the files we fopen().  From Debian [1].

[1] http://sources.debian.net/src/wmget/0.6.0-5/debian/patches/
    fix_resource_leaks.patch/

wmget/configure.c

@@ -373,6 +373,7 @@ static void load_rcfile (ServerConfig *cfg)
 
     if ((rcfp = fopen (rcfile, "rt"))) {
         read_rcfile (rcfp, cfg);
+        fclose (rcfp);
     } else {
         /* rcfiles are fully optional... */
         debug_sys ("Could not open rcfile '%s'", rcfile);

wmget/retrieve.c

@@ -98,6 +98,7 @@ void write_error_file (Job *job, const char *msg)
     fprintf (error_file, " To file: %s\n", job->options.save_to);
     fprintf (error_file, " Error: %s\n", msg);
     fprintf (error_file, " (" WMGET_VERSION_BANNER ")\n");
+    fclose (error_file);
 }