Bump VB and LV requirements, minor syncmul adjustments

[chriselrod]

I made a threading adjustment that broke things; was fixed with VectorizationBase 0.20.16.
I really should get around to setting up BuildKite to automate integration testing, instead of having to manually run tests on all down stream packages to see if things work.

VectorizationBase isn't a pleasant package to write unit tests for on it's own, since much of the code is less "made for humans" and more "made for LoopVectorization", so it's more natural to test via running @(t)turbo code.

[codecov]

Codecov Report

Merging #96 (af923dd) into master (0292d3f) will decrease coverage by 4.80%.
The diff coverage is 94.23%.

@@            Coverage Diff             @@
##           master      #96      +/-   ##
==========================================
- Coverage   86.60%   81.79%   -4.81%     
==========================================
  Files          11       11              
  Lines         724      736      +12     
==========================================
- Hits          627      602      -25     
- Misses         97      134      +37     

Impacted Files	Coverage Δ
src/matmul.jl	81.27% <92.59%> (-9.10%)	⬇️
src/complex_matmul.jl	100.00% <100.00%> (ø)
src/funcptrs.jl	100.00% <100.00%> (ø)
src/macrokernels.jl	89.55% <100.00%> (+1.31%)	⬆️
src/utils.jl	67.64% <100.00%> (ø)
src/memory_buffer.jl	36.84% <0.00%> (-31.58%)	⬇️
src/global_constants.jl	50.00% <0.00%> (-10.00%)	⬇️

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