lib/spiflash: do not spin on busy if no cb given
lib: add strchr, strcmp, strncmp
usb: add IAD support
usb/cdc: add IAD, call, and ACM descriptors
lib: add strchr, strcmp, strncmp
lib: use C function syntax
mk/linkdep: use uniq for uniformity
use "extern" variables in headers
lib/spiflash: add device erase
lib/stdio: increase buffer size
flash: fix K20 flash writing

Reported-by: bgamari