mousepad: inherit gsettings

When launch mousepad, it fails with:

| glib-gio-error setting schema 'org.xfce.mousepad' is not installed

It needs to call glib-compile-schemas to compile its schema file.
Inherit gsettings to fix it.

Signed-off-by: Kai Kang <kai.kang@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>