Build with -Wshadow
Change build directory for debug builds
Change function orger in firmware code
Fix shadow declaration in main.c
Cosmetic changes
Change --wait to take argument only in long form
Add current mode detection to teensy_handle_t

Use teensy_mode(h) to detect current mode, needed before using
any Teensy function. Replaces teensy_programmer. Turn teensy_mode_t
into an enum.
Rename teensy_write to teensy_program