libgnome: fix compile

error message was:
| gnome-program.c: In function 'gnome_program_init_common':
| gnome-program.c:2067:2: error: implicit declaration of function 'g_atexit' [-Werror=implicit-function-declaration]

Signed-off-by: Andreas Müller <schnitzeltony@googlemail.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>