Make verify_consumed consume trailing LWs.

This doesn't add any value yet, but starts paving the way for removing
LWS compacting from the parsing (unfortunately it seems to introduce
more problems than it solves).
Mark some functions public that should have been.
Simplify a common end-of-header parsing pattern.
Add some media-type (Content-Type header) tests.
Add some ETag helper functions and tests.
Merge.
Fix up etag compilation failures.

(That's what you get, working on an ARM machine
where you can't compile Rust code. :-( )
Make entity-tag W/ case insensitive (fixes a test).
Fix up media-type tests, ignoring some broken ones.
Add a quickcheck rule for fast test running.
Merge.