revlogv2: temporarily forbid inline revlogs
See inline comments. I plan to fix the underlying issue before revlogv2 is
stabilized.
Differential Revision: https://phab.mercurial-scm.org/D10030
To run the tests, do:
cd tests/
python run-tests.py
See https://mercurial-scm.org/wiki/WritingTests for
more information on writing tests.