Use 64-pin STM32L processor. Shrink board to 4.5 x 3.75

Use 64-pin STM32L processor. Shrink board to 4.5 x 3.75

Looks like we'll be able to use 64-bit processors almost everywhere,
so switch to that pinout for this product as well.

One proposed case, the Pelican 1120 has only about 3.875" clearance
between the two edges of the panel frame. Shrink the board to make
it fit.

Signed-off-by: Keith Packard <keithp@keithp.com>