MINOR: acl/pattern: use types different from int to clarify who does what.

MINOR: acl/pattern: use types different from int to clarify who does what.

We now have the following enums and all related functions return them and
consume them :

   enum pat_match_res {
	PAT_NOMATCH = 0,         /* sample didn't match any pattern */
	PAT_MATCH = 3,           /* sample matched at least one pattern */
   };

   enum acl_test_res {
	ACL_TEST_FAIL = 0,           /* test failed */
	ACL_TEST_MISS = 1,           /* test may pass with more info */
	ACL_TEST_PASS = 3,           /* test passed */
   };

   enum acl_cond_pol {
	ACL_COND_NONE,		/* no polarity set yet */
	ACL_COND_IF,		/* positive condition (after 'if') */
	ACL_COND_UNLESS,	/* negative condition (after 'unless') */
   };

It's just in order to avoid doubts when reading some code.