White List: Various fixes

Fix compilation with --enable-debug flag
Add a test for gupnp_white_list_remove_entry
Add test-white-list in .gitignore file

https://bugzilla.gnome.org/show_bug.cgi?id=706326
White List: Fix remove entry function

Remove the GList element found by g_list_find_custom.

https://bugzilla.gnome.org/show_bug.cgi?id=706326