CLEANUP: regex: remove outdated support for regex actions

The support for reqrep and friends was removed in 2.1 but the
chain_regex() function and the "action" field in the regex struct
was still there. This patch removes them.

One point worth mentioning though. There is a check_replace_string()
function whose purpose was to validate the replacement strings passed
to reqrep. It should also be used for other replacement regex, but is
never called. Callers of exp_replace() should be checked and a call to
this function should be added to detect the error early.
diff --git a/include/common/regex.h b/include/common/regex.h
index 066f07e..cecfbd9 100644
--- a/include/common/regex.h
+++ b/include/common/regex.h
@@ -61,18 +61,9 @@
 #endif
 };
 
-/* what to do when a header matches a regex */
-#define ACT_ALLOW	0	/* allow the request */
-#define ACT_REPLACE	1	/* replace the matching header */
-#define ACT_REMOVE	2	/* remove the matching header */
-#define ACT_DENY	3	/* deny the request */
-#define ACT_PASS	4	/* pass this header without allowing or denying the request */
-#define ACT_TARPIT	5	/* tarpit the connection matching this request */
-
 struct hdr_exp {
     struct hdr_exp *next;
     struct my_regex *preg;		/* expression to look for */
-    int action;				/* ACT_ALLOW, ACT_REPLACE, ACT_REMOVE, ACT_DENY */
     const char *replace;		/* expression to set instead */
     void *cond;				/* a possible condition or NULL */
 };
@@ -92,8 +83,6 @@
 struct my_regex *regex_comp(const char *str, int cs, int cap, char **err);
 int exp_replace(char *dst, unsigned int dst_size, char *src, const char *str, const regmatch_t *matches);
 const char *check_replace_string(const char *str);
-const char *chain_regex(struct hdr_exp **head, struct my_regex *preg,
-			int action, const char *replace, void *cond);
 
 /* If the function doesn't match, it returns false, else it returns true.
  */
diff --git a/src/regex.c b/src/regex.c
index 6b86b03..195f9a7 100644
--- a/src/regex.c
+++ b/src/regex.c
@@ -124,33 +124,6 @@
 }
 
 
-/* returns the pointer to an error in the replacement string, or NULL if OK */
-const char *chain_regex(struct hdr_exp **head, struct my_regex *preg,
-			int action, const char *replace, void *cond)
-{
-	struct hdr_exp *exp;
-
-	if (replace != NULL) {
-		const char *err;
-		err = check_replace_string(replace);
-		if (err)
-			return err;
-	}
-
-	while (*head != NULL)
-		head = &(*head)->next;
-
-	exp = calloc(1, sizeof(*exp));
-
-	exp->preg = preg;
-	exp->replace = replace;
-	exp->action = action;
-	exp->cond = cond;
-	*head = exp;
-
-	return NULL;
-}
-
 /* This function apply regex. It take const null terminated char as input.
  * If the function doesn't match, it returns false, else it returns true.
  * When it is compiled with JIT, this function execute strlen on the subject.