MEDIUM: acl/pattern: use the same direction scheme

MEDIUM: acl/pattern: use the same direction scheme

Patterns were using a bitmask to indicate if request or response was desired
in fetch functions and keywords. ACLs were using a bitmask in fetch keywords
and a single bit in fetch functions. ACLs were also using an ACL_PARTIAL bit
in fetch functions indicating that a non-final fetch was performed, which was
an abuse of the existing direction flag.

The change now consists in using :
  - a capabilities field for fetch keywords => SMP_CAP_REQ/RES to indicate
    if a keyword supports requests, responses, both, etc...
  - an option field for fetch functions to indicate what the caller expects
    (request/response, final/non-final)

The ACL_PARTIAL bit was reversed to get SMP_OPT_FINAL as it's more explicit
to know we're working on a final buffer than on a non-final one.

ACL_DIR_* were removed, as well as PATTERN_FETCH_*. L4 fetches were improved
to support being called on responses too since they're still available.

The <dir> field of all fetch functions was changed to <opt> which is now
unsigned.

The patch is large but mostly made of cosmetic changes to accomodate this, as
almost no logic change happened.