ENH: improve duck typing inside iscomplexobj

Both `iscomplexobj` and `isrealobj` now try to refer to the argument's
`dtype` attribute if it exists. This significantly extends the list of
types for which `iscomplexobj` returns correct results (including e.g.
scipy sparse matrices and pandas objects).

Extended the tests of the `iscomplexobj` routine for the following cases:
* simple scalars
* standard lists (test internal auto-conversion to numpy arrays)
* "Duck typing" for objects that define a dtype attribute (either
  referring to one of the existing numpy dtypes, or a custom dtype, as
  pandas does)

This fixes #7924

0 files changed, 0 insertions, 0 deletions