Problem: If autocmd pattern only contained `++once` handlers, and
all of them completed, then there would be an empty group
displayed by `:autocmd Foo`.
Solution: Delete the pattern if all of its commands were deleted.
Adds a new feature to :autocmd which sets the handler to be executed at
most one times.
Before:
augroup FooGroup
autocmd!
autocmd FileType foo call Foo() | autocmd! FooGroup * <buffer>
augroup END
After:
autocmd FileType foo once call Foo()
It is otherwise impossible to determine which test failed sanitizer/valgrind
check. test/functional/helpers.lua module return was changed so that tests which
do not provide after_each function to get new check will automatically fail.
