Bump the minimum required Julia version to 1.6

[martinholters]

Ref. #524 (review)

I don't think we have to worry anymore about versions older than 1.6 (current LTS released almost three years ago).

[wheeheee]

Might want to add stdlibs to compat at the same time, to get JuliaRegistrator to automerge into the general registry when you wish to release.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (9de4c0c) 97.49% compared to head (7640b8d) 97.49%.
Report is 1 commits behind head on master.

Additional details and impacted files

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##           master     #532   +/-   ##
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  Coverage   97.49%   97.49%           
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  Files          18       18           
  Lines        3078     3078           
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  Hits         3001     3001           
  Misses         77       77           

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[ViralBShah]

Can we remove some of the old versions in FFTW, OffsetArrays, Polynomials, Reexport, and SpecialFunctions?

I just pushed a commit to see if pushing aggressively will work with 1.6.

[ViralBShah]

We may want to do this after #458 merges so that we can adopt these new deps from 0.8-dev.

[ViralBShah]

@martinholters Note I bumped DSP.jl version to 0.8.0 here which will go on master. Hence the next version tag will be 0.8.0 and we can pull in a few breaking changes as discussed in the Analog Filter PR.

[martinholters]

Can we remove some of the old versions in FFTW, OffsetArrays, Polynomials, Reexport, and SpecialFunctions?

I guess so. I doubt we have any dependents still requiring them - and if so, that would be a good opportunity to incentivize to update.

Also, we don't test whether we're actually still compatible with the old versions of out dependencies, so might be making false promises here.

Bottom line: Yes, lets drop the old versions from out compat.

We may want to do this after #458 merges so that we can adopt these new deps from 0.8-dev.

Hm? I mean yes, combing this compat bump with the version bump to 0.8 sounds reasonable (though not strictly necessary by semver, I believe), but why should that wait for #458?

[ViralBShah]

Agree we do not need to wait for the other PR to merge for the version bump. This seems like it is good to merge now.

[ViralBShah]

Merging this for now. We can always tweak as we go along.