REORG: acl/pattern: extract pattern matching from the acl file and create pattern.c

This patch just moves code without any change.

The ACL are just the association between sample and pattern. The pattern
contains the match method and the parse method. These two things are
different. This patch cleans the code by splitting it.
diff --git a/src/payload.c b/src/payload.c
index de6395f..4356025 100644
--- a/src/payload.c
+++ b/src/payload.c
@@ -16,6 +16,7 @@
 #include <proto/acl.h>
 #include <proto/arg.h>
 #include <proto/channel.h>
+#include <proto/pattern.h>
 #include <proto/payload.h>
 #include <proto/sample.h>