Fixes issue that prevents the autoloader from working when unit tests are executed in separate processes with "@preserveGlobalState" enabled
feature #416 Fixes autoloader issue (Class 'Swift_Mailer' not found in..) (NickStemerdink)

This PR was merged into the 5.1-dev branch.

Discussion
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Fixes autoloader issue (Class 'Swift_Mailer' not found in..)

Currently the autoloader fails when unit test are executed with the following conditions:
- Isolated processes
- Preserve global state

This is because in the subprocess the constant is preserved, but the autoload register will be clean. So the autoloader would not be added to any subprocess.

Commits
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7758184 Fixes issue that prevents the autoloader from working when unit tests are executed in separate processes with "@preserveGlobalState" enabled