usb-source.h: s/USB_MAINLOOP/GUSB_SOURCE/
usb-source.h: s/USB_MAINLOOP/GUSB_SOURCE/

robert-ancell/libgusb,hughsie/libgusb,nacho/libgusb,hughsie/libgusb,nacho/libgusb,hughsie/libgusb,robert-ancell/libgusb