Enable runtime controlled debug output.

[MattHeffron]

Currently only in make_X_keymap.
Output is to STDOUT (since the conditional compilation DEBUG did)

Medley branch: mth38--command-line-arg-to-support-maiko-runtime-debug adds command line argument support for this.

This is draft as it probably isn't generally applicable. OTOH, it's also relatively harmless (as of now).

[nbriggs]

Since this doesn't depend on anything other than the results from XGetKeyboardMapping (e.g., it doesn't reflect maiko's interpretation of its own table with respect to this), I think having this in a trivial extra program would be better - in the same way we ship programs like "tstsout.c" and "setsout.c"

[MattHeffron]

That's fine with me for the current output from initkbd.c.
If this is a useful concept/feature for maiko, should the changes in main.c be kept? (A separate PR?)

Specifically, being able to turn on some pre-defined debugging output without needing to rebuild.
Maybe also, do either bit-testing or exact value testing, vs. > threshold testing against the runtime_debug_level. (That would mean that it isn't a _level.)

If there's no value in this at all, then there's no need for Medley PR #2038

[nbriggs]

My choice would be something akin to (if not actually) DTrace probes. Before DTrace existed we used a very low-overhead always-on debugging probe mechanism which maintained a circular buffer of events which you could dump either in real-time, or extract from a core file. Anything that goes into the dispatch loop for the emulator needs to be carefully considered, and the probe mechanism should introduce the minimum possible latency.

[MattHeffron]

Close/delete this PR (and Medley PR 2038) as unnecessary (at least at this time).