mq: grab locks before starting a transaction

Merge with crew

extensions: load modules in module/__init__.py form. For example, convert=/path/to/convert now works.

test-patchbomb: sed -e may not work with extended regexps Non-GNU versions of the sed(1) utility (i.e. on Solaris or BSD) may not support extended regexps (i.e. including \| branches), or may need a special option to enable it (like -E instead of -e). Expand the sed RE in tests/test-patchbomb to fix running this test on FreeBSD and Solaris.