[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
[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