Clarify differences between / requirements for request and response CC directives

[mnot@…]

S 3.2 Cache-Control first sentence states that directives MUST be obeyed. This doesn't fit with a strategy of ignoring unhandled directives if you get a mixture of request and response directives in a message (which is still allowed in the ABNF).

Furthermore, the BNF doesn't make it clear that request and response directives shouldn't be intermixed;

Cache-Control-v = 1#cache-directive

cache-directive = cache-request-directive

/ cache-response-directive

[julian.reschke@…]

proposed patch for part 6

[julian.reschke@…]

From [827]:

Clarify differences between / requirements for request and response CC directives (see #168)