Add legacy

[Danile71]

[codecov[bot]]

Codecov Report

Merging #823 (0354281) into dev (7d6aabe) will decrease coverage by 0.00%. The diff coverage is n/a.

@@            Coverage Diff             @@
##              dev     #823      +/-   ##
==========================================
- Coverage   96.74%   96.73%   -0.01%     
==========================================
  Files          20       20              
  Lines        1933     1931       -2     
==========================================
- Hits         1870     1868       -2     
  Misses         46       46              
  Partials       17       17              

Impacted Files	Coverage Δ
features2d.go	100.00% <0.00%> (ø)

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[deadprogram]

@Danile71 could you please add some smoke tests now for the legacy functions? Thanks!