Problem: Crash when an autocommand changes a quickfix list. (Dominique)
Solution: Check wether an entry is still valid. (Yegappan Lakshmanan,
Hirohito Higashi)
Problem: Need several lines to verify a command produces an error.
Solution: Add assert_fails(). (suggested by Nikolay Pavlov)
Make the quickfix alloc test actually work.
Problem: Alloc_id depends on numbers, may use the same one twice. It's not
clear from the number what it's for.
Solution: Use an enum. Add a function to lookup the enum value from the
name.
Problem: New style tests are executed in arbitrary order.
Solution: Sort the test function names. (Hirohito Higashi)
Fix the quickfix test that depended on the order.
Problem: It is not possible to test code that is only reached when memory
allocation fails.
Solution: Add the alloc_fail() function. Try it out with :vimgrep.
