Remove unused return value, because collecting_queries_for_explain isn't public API.
Merge pull request #9565 from kennyj/remove_unused_return_value

Remove unused return value, because collecting_queries_for_explain isn't public API.
Add DebugHelperTest
Merge pull request #9574 from robertomiranda/debug_helper_test

Add DebugHelperTest
Add missing require to debug helper test
CHANGELOG entry for improved singularizing of singulars.

Closes #9559.

The actual patch was added with #4719
Merge pull request #9581 from senny/9559_changelog_singularizing_singular

CHANGELOG entry for improved singularizing of singulars.