Add dedicated symbolic series tests

[rwst]

This adds a testsuite to the tests/ directory.

Component: symbolics

Author: Ralf Stephan

Branch/Commit: 5d93be8

Reviewer: Marc Mezzarobba

Issue created by migration from https://trac.sagemath.org/ticket/21730

[rwst]

Branch: u/rws/add_dedicated_symbolic_series_tests

[rwst]

New commits:

579db7d

21730: Add dedicated symbolic series tests

[rwst]

Commit: 579db7d

[sagetrac-git]

Changed commit from 579db7d to 5d93be8

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

f2952bd	add cot/sec/csc tests
5d93be8	added coth/sech/csch

[mezzarobba]

comment:4

The new tests pass, and I double-checked them all. I would have expected these tests somewhere under sage/symbolic rather that in sage/tests, but I don't think it matters too much.

[mezzarobba]

Reviewer: Marc Mezzarobba

[vbraun]

Changed branch from u/rws/add_dedicated_symbolic_series_tests to 5d93be8