Remove unintended connections between some doctests
Test ex_unit before doctests
Implement extended doctest sessions. Closes #1020
Little refactoring
Add a test for leaking vars
Remove unused debug output
Make test_doctest target depend on test_ex_unit
Deduplicate test generation code
Add a couple of comments explaining decisions
Clean up the docs for doctests
Minor formatting fixes
Review doctests in stdlib to use extended doctests
Test doctests for ExUnit.CaptureIO
Revert "Make test_doctest target depend on test_ex_unit"

This reverts commit b2d0355ef980eeae2d257aa933b9f416bbd931b9.

Better keep the tests separate as before. It is sufficient to have
ex_unit tests invoked before doctest tests when doing the full `make test`
Don't test DocTest's doctests
Include location info in the multiple exceptions error
Add space to error message in mix
Merge pull request #1135 from mururu/add-space

Add space to error message in mix
Add tests for %w(BigAtom)a mentioned in #1131
Merge pull request #1128 from alco/1020-extended-doctest

Implement extended doctests