MINOR: map: Add regex matching replacement

This patch declares a new map which provides a string based on
a string with back references replaced by the content matched
by the regex.
diff --git a/include/proto/pattern.h b/include/proto/pattern.h
index 0a132f2..9c93db9 100644
--- a/include/proto/pattern.h
+++ b/include/proto/pattern.h
@@ -67,6 +67,7 @@
 int pat_idx_list_ptr(struct pattern_expr *expr, struct pattern *pat, char **err);
 int pat_idx_list_str(struct pattern_expr *expr, struct pattern *pat, char **err);
 int pat_idx_list_reg(struct pattern_expr *expr, struct pattern *pat, char **err);
+int pat_idx_list_regm(struct pattern_expr *expr, struct pattern *pat, char **err);
 int pat_idx_tree_ip(struct pattern_expr *expr, struct pattern *pat, char **err);
 int pat_idx_tree_str(struct pattern_expr *expr, struct pattern *pat, char **err);
 int pat_idx_tree_pfx(struct pattern_expr *expr, struct pattern *pat, char **err);
@@ -174,6 +175,7 @@
  * and restores the previous character when leaving.
  */
 struct pattern *pat_match_reg(struct sample *smp, struct pattern_expr *expr, int fill);
+struct pattern *pat_match_regm(struct sample *smp, struct pattern_expr *expr, int fill);
 
 /*
  * pattern_ref manipulation.