A bit of code clean-up and a lot of test clean-up around userdiff
area.
* ab/userdiff-tests:
blame tests: simplify userdiff driver test
blame tests: don't rely on t/t4018/ directory
userdiff: remove support for "broken" tests
userdiff tests: list builtin drivers via test-tool
userdiff tests: explicitly test "default" pattern
userdiff: add and use for_each_userdiff_driver()
userdiff style: normalize pascal regex declaration
userdiff style: declare patterns with consistent style
userdiff style: re-order drivers in alphabetical order