fix ABNF for If-Match and If-None-Match

[reschke]

...not to special-case "*" as top-level construct.

[mnot]

Also need to fix things like

when the field value is "*"

to something like

when the field value contains "*"

[mnot]

Discussed; intent is to add a note at the end of each section pointing out that the behaviour of multiple/mixed stars is undefined, and that this is a lame way to specify a field.