Deprecate the top-level functions in path.py
Remove deprecated code
Use new warn_deprecated helper function and decorator where appropriate.
Warn about incompleteness of CocoaAgg backend
Remove the Fltk backend
Remove the EMF backend
Remove FltkAgg from comment
Fix typo
Remove commented out stuff
Remove misleading sentence.
Fix some typos pointed out in #2026.
Merge pull request #2026 from mdboom/deprecations-pre-13

Major deprecations and housecleaning for v1.3