ir_nec: Add dumps for corner cases (timing tolerance, last packet decode)

ir_nec: Add dumps for corner cases (timing tolerance, last packet decode)

Add file joy_it_sbc_irc01_all.sr which exceeds the previous 5% limit for
timing tolerances and would not decode at all.

Add file joy_it_sbc_irc01_enter_no_repeat.sr which lacks a repeat code
after a key press, which earlier decoder versions would have failed to
decode.

[ gsi: rename probes, add README, rephrase commit message ]