Merge changes I9b77c105,I0b369d16,I59602c20,Iae4f3d55

* changes:
  adbd: implement a nonblocking USB Connection.
  adbd: rename daemon/usb.cpp to daemon/usb_legacy.cpp.
  adbd: open functionfs ep0 as O_RDWR.
  adbd: extract functionfs fd creation.