[module] sonar_maxboitx -usable with fixedwing or rotor -output: distance in m (the module sonar_maxbotix_booz) is unefected
[nps] fix time: initialize sys_time by adding missing PERIPHERALS_AUTO_INIT
cleaned the code and renamed the files to be consistend in to sonar_adc
[makefile] print paparazzi_version when building sim, remove throwing error on old UART_NR configure
[conf] remove nps settings file from Quad_LisaM2 example airframe, you can only include it if compiling nps
course is now correctly calculated
sonar_offset to m and clean up
Merge pull request #378 from TobiasMue/sonar

[module] sonar_adc -usable with fixedwing or rotor and distance output
[mavlink] fix crc function names for compatibility with libocm3
[peripherals] spi transactions: always set clock divider and bitorder
[stm32][spi] removed commented/unused stuff
[dox] update/add some more doxygen comments
[airborne] std.h: define NULL if not already done
[spi][stm32] updated handling of different transaction lengths
- now tx buffer sizes are independent of rx buffer sizes
- uses a second dummy dma transmit transfer triggered of the
  first transmit dma ISR when 0 < tx_len < rx_len
[spi][stm32] Added second dummy buffer dma handling for rx too
- handled in the same way as tx
- simplifies completion interrupt timing, clearing registers and
  running callback and deselecting slave at the right time,
  AFTER the last byte is fully transmitted.
- Also updated comments.
[stm32][spi] refactor: spi_next_transaction function
[stm32][spi] refactor: spi_configure_dma function
[stm32][spi] style
[stm32][spi] removed other_dma_finished, always run rx dma till the end of transaction
[stm32][spi] rename x_use_dummy_dma to x_extra_dummy_dma