* pico_stdio_usb: be more explicit about includes, fix warning (#257)
* pico_base: NDEBUG backwards for absolute_time_t (#255)
* pico_util: missing extern C in queue.h (#249)
* build: remove -march which was masking -mcpu, now SVC available (#253)
- setting baud rate to magic value (default=1200) will cause a reset to BOOTSEL mode
- a VENDOR interface along side the CDC interface can be used to reset via refular flash boot, or into
BOOTSEL mode with control for the reset_usb_boot parameters for the latter
either method can be configured/enabled/disabled via #define