applet.jtag.svf: new applet.

protocol.jtag_svf: new protocol.

applet.xc9500: make programming way faster than anyone would want. Also, improve robustness of error checking, and document spurious failures during programming. (Recycled units? Quite possibly...)

applet.xc9500: doc clarification.

applet.jtag.xc9500: new applet.

applet.jtag: add run_test_idle() function.

gateware.fx2: add missing import.

applet.jtag: fix incorrect doc.

applet.jtag: unbreak enumerate-ir operation, handle DR[0] case.

applet.jtag: implement (very danger/u/s) enumerate-ir operation.