[gpio] move gpio_setup_x declarations to implementation

properly document that you can actually set multiple gpios at a time
[lpc21] implement gpio functions
[lcp21] fix gpio_toggle
[datalink] w5100: arch indep gpio functions for drdy pin
[test] fix test_sys_time_x
[boards] tiny/twog: fix led color comments
Merge pull request #651 from paparazzi/gpio

Gpio interface improvements

Common gpio functions for lpc21 and stm32 architectures like:
- gpio_setup(GPIOA, GPIO1)
- gpio_clear(GPIOA, GPIO1)
- gpio_setup_output(GPIOA, GPIO1)
- gpio_setup_input(GPIOA, GPIO1)

you can also set multiple gpios at once, e.g.: `gpio_set(GPIOA, GPIO1 | GPIO2)`
[modules] Removed GPS_PORT_ID, added comments, and compile warnings if GPS_PORT_ID is defined.

closes #653
closes #647
[conf] FLASH_MODE cleanup
[modules] fix gps_ubx_ucenter debug print

- use DEBUG_PRINT macro (that is only active if DEBUG_GPS_UBX_UCENTER) instead of printf
- add missing default case
[airborne] only cosmetic cleanup: convert leading tabs to spaces
[ins] fix ins_reset_local_origin ifndef GPS_USE_LATLONG

divide utm in int/cm by float (100.0f instead of 100)

while at it, explicitly use floats in some more conversions (technically 100. is a double)
[conf] flash_modes: fix board regexes
[stm32][i2c] enable correct error interrupts
[peripherals] fix dox for l3gd20
start bringing changelog up-to-date
[include] message_pragmas.h
[ins] add warning if obsolete INS_BARO_SENS is defined
[baro] print information about which baro_board sensor is used
[messages] fix order in HFF_DBG