Non-allocating adjoint for Hankel

[jishnub]

Also, specialize issymmetric/ishermitian to return in O(1) time.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.88%. Comparing base (ee9e796) to head (5474418).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #137      +/-   ##
==========================================
+ Coverage   93.87%   93.88%   +0.01%     
==========================================
  Files           9        9              
  Lines         963      965       +2     
==========================================
+ Hits          904      906       +2     
  Misses         59       59              

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