The new control interface command "REQ_BEACON <STA addr>
[req_mode=<mode>] <beacon request>" can now be used to request hostapd
to transmit a measurement request to request a beacon report from an
associated STA. This command returns the assigned dialog token (1-255)
or FAIL on failure.
Signed-off-by: Jouni Malinen <j@w1.fi>