Build option to disable building non-JSON module

[ericonr]

I think it would be nice if we could only build the JSON module, that way site-policy on logging format can be easily enforced at build time as well. Is this a change that would be accepted?

If we do it, I would also consider adding aliases for the commands/variables for the original functions to apply for the JSON ones as well; that way startup scripts using the old version could be upgraded automatically. Would that make sense, or would it be better to keep the current split?

[anjohnson]

I forget how hard it would be to disable building the old code, although without checking it doesn't seem like it should be tricky. I'd be fine with allowing that, set a variable in the configure/CONFIG_SITE file to control which parts get built.

I'd rather not have the old commands generate the new log format though, that could cause breakage at sites that transition and set up a new log port for the new format.

[simon-ess]

It's a good idea to try do this, I think. This could fit in the upcoming codeathon.

[ralphlange]

My 2cts: This is messy and not getting better.

Different internal APIs, different dependencies leading to different target systems, different output formats, and a separate code base.
Should have been a separate module to begin with.