udev-rules: check token delimiters

udev-rules: check token delimiters

When udev_rules_parse_file() is called by udevadm verify, issue warnings
about the following conditions in udev rules:
* the first token in the rule is preceded with a comma
* the last token in the rule is followed by a comma
* there is no comma between tokens
* there is no whitespace between tokens
* there is more than a single comma between tokens
* there is whitespace between a token and a comma
* there is no whitespace after comma