parser/printer/tests: Add :delmarks command parser
parser: Parse :debug command as :*do* iterator command
parser/tests: Use parse_rest_line to parse :delcommand
parser/tests: Add :display/:registers parsing support
parser/tests: Add support for parsing :diffget/:diffput
parser/printer/tests: Add :digraphs parsing support
parser/printer/tests: Add :doautocmd parsing support
parser/tests: Add support for parsing :doautoall

It is basically the same thing as :doautocmd
parser/tests: Record the fact that :drop parsing is already supported
parser/printer: Add :earlier/:later commands support
tests: Add :earlier/:later tests