glib-2.0: Add abs() to float and double
glib-2.0: Add abs() to float and double

https://bugzilla.gnome.org/show_bug.cgi?id=764663

GNOME/vala,frida/vala,frida/vala,frida/vala,GNOME/vala,GNOME/vala,frida/vala,GNOME/vala,frida/vala