tomlc99 is unsupported but upstream fuzzer bug was reported

[garlick]

Problem: cktan/tomlc99#97 was reported upstream, but tomlc99 is no longer supported. We should consider whether we need a fix here.

p.s. I don't think this overlaps with the tomlc99 bugs fixed in #221 but I could be wrong.

[grondo]

I think the validation added to tomltk in #221 works around these issues because it adds max bracket and dotted key nesting before sending TOML off to be parsed by libtomlc99. (I think the max nesting is 32, whereas the proof of concept in that issue was >100K nesting (I think?)). These issues showed up as hangs during fuzzing since I don't think the fuzzer lets individual tests run all that long before killing them off.

We should update our TOML parser to a supported version at some point. It is nice that we'll still be able to use the tomltk wrapper. We can remove the validation guards and rerun the unit tests that reproduced all these parsing corner cases.

[grondo]

Going to close this as fixed. Please reopen if you're convinced this isn't fixed by #221 @garlick!