- nanonote.c (nanonote_open): increased register window to include clock
and MMC controller registers
- nanonote.c (gpio_function): set a pin to function or GPIO
- nanonote.c (nanonote_initpgm, nanonote_parseextparams): accept the
extended option clk=N where N is the clock frequency in (whole) MHz
- nanonote.c (nanonote_enable): if the clock option is set, switch CLK
to function and output the specified clock