cmake: require at least version 3.16

[sergiud]

Fixes #705

[codecov-commenter]

Codecov Report

Merging #758 (910133f) into master (52354b2) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #758   +/-   ##
=======================================
  Coverage   72.85%   72.86%           
=======================================
  Files          17       17           
  Lines        3224     3225    +1     
=======================================
+ Hits         2349     2350    +1     
  Misses        875      875           

Impacted Files	Coverage Δ
src/logging.cc	73.88% <0.00%> (+0.02%)	⬆️

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