[stm32] timer_get_frequency helper function
[stm32] adc timer frequency

The ADC was running at different frequencies, depending on which timer was used
(e.g. TIM1 is on high speed APB2, TIM2 on low speed APB1).

And seems it was running a LOT slower on F4.
TRGO is used to trigger ADC conversion, which generated upon reaching period reload value.
That was 0xFFFF on F4 and 0xFF on F1.

So it seems that before this commit we had:

F1:
----
All timers normally all run with 72MHz as we have set it up...
* with prescaler of 8: we get 72MHz/9 = 8MHz timer freq
* with period of 0xFF: ADC conversions at 8MHz / 255 = ~31kHz

F4:
----
TIM1 is on ABP2 witch means twice as fast as e.g. TIM2 on APB1:
timers run at 2xAPB frew: on high speed bus 168MHZ and on low speed with 84MHz
* with prescaler of 0x53: 168MHz/84 = 2MHz timer freq for TIM1 (1MHz for TIM2)
* with period of 0xFFFF: 2MHZ / 0xFFFF = ~30Hz (15Hz for TIM2)

That is a difference of factor 1000 between F1 and F4!!

Now it will run at same freq regarless of wich TIM is used (and same on F1/F4):
default ADC update freq: ADC_TIMER_FREQUENCY / ADC_TIMER_PERIOD = 2MHz / 1000 = 2kHz
[stm32] define TIM9 and TIM12
Merge pull request #734 from paparazzi/stm32_timer_get_frequency

[stm32] timer_get_frequency helper function
[rotorcraft] RC input: zero yaw command if throttle is zero

should fix #736
[rotorcraft] include and dox cleanup
update CHANGELOG
[stm32] fix get_timer_frequency

forgot to remove #if ADVANCED_TIMERS which I added when using it in locm3 timer_common_all.c
[adc] remove adc_new_data_trigger and update test_adc
[rotorcraft] prevent motor arming in kill mode

closes #740
[navstik] Added a new board
[stm32] fix compilation on F1 boards
[boards] minor fixes for navstik
[ins] properly define INS_VFF_R_GPS

closes #741
[electrical] min bat level check

This allows for detecting when voltage is too low to be a real reading and treats it as invalid.
The GCS shows BAT LOW INVALID.
The ap does not set bat_low or bat_critical if the reading was never valid.
But once a valid voltage is read then low level checking is always done.

closes #745
[fixedwing] stabilization adaptive: remove obsolete declarations

Thanks Loic.
[server] try to update AGL even if GPS is lost

close #742
[tools] flash via bmp: reset and detach from target after uploading

closes #746
[modules] Fix include related to stabilization_attitude in gain_scheduling to
reflect current file nomenclature.
[gcs] Display AP mode forward (FWD) when selected instead of UNK