MEDIUM: http: make all ACL fetch function use acl_prefetch_http()

MEDIUM: http: make all ACL fetch function use acl_prefetch_http()

All ACLs which need to process HTTP contents first call this function which
performs all the preliminary tests and also triggers the request parsing if
needed. A macro was written to simplify the code.

As a side effect, it's not required anymore to check for the HTTP ACL before
checking for HTTP contents.