Initial Rev C IO cell schematic.

applet: move all applets to individual subdirectories. Applets are about to gain test fixtures, which would be really annoying to place out-of-tree, I think. Also, consistent relative import paths are a bonus.

applet.spi.flash_avr: add missing @synthesis_test.

access.simulation.multiplexer: implement FIFO flush, as a stub.

applet.spi.flash_avr: fix build().

applet.jtag.pinout: fix test_build().

support.endpoint: cancel recv() on end-of-stream.

applet.spi.{master,flash_25c}: add missing @synthesis_test.

setup: fix typo.

applet.jtag.{mec16xx,xc9500}: fix typo.