Add missing include for geteuid() missing declaration
xtm_process_window_show_swap_usage() in process-window.
Fix various compiler warnings from main.c task-manager.c and
app-manager.c.
Add optional link on libwnck (default=yes) and build a new object from
app-manager.c to keep an up to date list of applications with their name
and icon. Use it inside the task manager object to display inside the
tree view.