Fix cordtst2.tmp file deletion in cordtest on Windows

On Windows, remove() operation deletes the file only if the file is
closed.

* cord/tests/cordtest.c (test_extras): Do not call remove(FNAME2).
* cord/tests/cordtest.c (main): Call GC_gcollect() and remove(FNAME2)
just before printing the test succeeded; add comment.

cord/tests/cordtest.c

@@ -287,9 +287,6 @@ static void test_extras(void)
         /* But we cannot call fclose as it might lead to double close.   */
         fprintf(stderr, "WARNING: remove failed: " FNAME1 "\n");
     }
-    if (remove(FNAME2) != 0) {
-        fprintf(stderr, "WARNING: remove failed: " FNAME2 "\n");
-    }
 }
 
 static int wrap_vprintf(CORD format, ...)
@@ -402,6 +399,11 @@ int main(void)
     test_basics();
     test_extras();
     test_printf();
+
+    GC_gcollect(); /* to close f2 before the file removal */
+    if (remove(FNAME2) != 0) {
+        fprintf(stderr, "WARNING: remove failed: " FNAME2 "\n");
+    }
     CORD_fprintf(stdout, "SUCCEEDED\n");
     return 0;
 }