Leave clause in case the handler can fail
Allow only one process handler per process
Move from module_not_found to the more generic handler_not_found
Do not wrap process handlers in a tuple
Move from already_added to already_present
Deprecate monitor option in GenEvent
Tidy up GenEvent docs and test suite
Test :sys functions with GenEvent
Make the regex type non-opaque
Fix IEx test
Lowercase drive letters from cwd, closes #2747
Update CHANGELOG
Ensure we don't look up inexisting variables for default args