MEDIUM: pattern: The expected type is stored in the pattern head, and conversion...

MEDIUM: pattern: The expected type is stored in the pattern head, and conversion is executed once.

This patch extract the expect_type variable from the "struct pattern" to
"struct pattern_head". This variable is set during the declaration of
ACL and MAP. With this change, the function "pat_parse_len()" become
useless and can be replaced by "pat_parse_int()".

Implicit ACLs by default rely on the fetch's output type, so let's simply do
the same for all other ones. It has been verified that they all match.