Fix performance regression

[YingboMa]

Fixes #571

julia> @btime solve($probs,$(Tsit5())); # master
  2.981 ms (60568 allocations: 4.10 MiB)

julia> @btime solve($probs,$(Tsit5())); # PR
  487.315 μs (2664 allocations: 473.02 KiB)

[coveralls]

Coverage decreased (-21.04%) to 46.683% when pulling 85e2dcf on myb/perf into f9206b0 on master.

[codecov]

Codecov Report

Merging #574 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #574      +/-   ##
==========================================
+ Coverage   68.87%   68.87%   +<.01%     
==========================================
  Files          81       81              
  Lines       23997    23998       +1     
==========================================
+ Hits        16527    16528       +1     
  Misses       7470     7470

Impacted Files	Coverage Δ
src/misc_utils.jl	62.85% <100%> (+1.09%)	⬆️

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[devmotion]

By the way, did you test whether the different implementations (that were introduced to circumvent some performance regression due to broadcasting: #107 (comment)) are still required?

[dkarrasch]

What types of internalnorm can be used? I thought one could, for instance, define an internalnorm that computes the norm based on only few of the components. That couldn't be called on numbers then?

[devmotion]

At the moment you have to define a scalar norm as well but that will be changed in the next DiffEq release. There's a discussion about this issue in #569.

[YingboMa]

By the way, did you test whether the different implementations are still required?

Yes, it is still needed.

[ChrisRackauckas]

Sweet, I find this to be cleaner as well.

[dkarrasch]

Can we please get a version tag for this fix? Or are there more things currently in the pipeline?

[ChrisRackauckas]

Release made