Suppress deprecated warnings

    benchmark.c: In function 'bench_init':
    benchmark.c:26:5: warning: 'g_thread_init' is deprecated (declared at /usr/include/glib-2.0/glib/deprecated/gthread.h:260) [-Wdeprecated-declarations]
    benchmark.c:28:3: warning: 'g_type_init' is deprecated (declared at /usr/include/glib-2.0/gobject/gtype.h:669) [-Wdeprecated-declarations]