Correctly position text with nonzero descent with afm fonts / ps output.

[anntzer]

See e.g.

rcParams["ps.useafm"] = True
text(.5, .5, "qk")
axhline(.5)
savefig("/tmp/test.ps")

Previously the bottom of the tip of the "q" would be on the baseline;
now the baseline is correctly positioned.

(I picked a relatively generic name for the test because we could later
update the baseline image "in place" for more afm tests.)

PR Summary

PR Checklist

• Has pytest style unit tests (and pytest passes).
• Is Flake 8 compliant (run flake8 on changed files to check).
• New features are documented, with examples if plot related.
• Documentation is sphinx and numpydoc compliant (the docs should build without error).
• Conforms to Matplotlib style conventions (install flake8-docstrings and pydocstyle<4 and run flake8 --docstring-convention=all).
• New features have an entry in doc/users/next_whats_new/ (follow instructions in README.rst there).
• API changes documented in doc/api/next_api_changes/ (follow instructions in README.rst there).

[tacaswell]

This line came in via 839434c with the comment that it is fixing an aligment issues, but it is not clear what issues. The code around this has also been changed quite a bit as we used to have draw_text and draw_unicode and now just draw_text (they got merged in f9a68c1).

I agree that the proposed change is correct and it is not worth doing further digging to sort out what was being fixed previously.

[QuLogic]

This seems a bit leaky; I wonder if we should trim the title to just the filename?

[anntzer]

As a general matter (i.e. not just for tests), I would say yes.