BUILD: http_act: use __fallthrough in parse_http_del_header()
This avoids one build warning when preprocessing happens before compiling
with gcc >= 7.
diff --git a/src/http_act.c b/src/http_act.c
index b370861..d4da439 100644
--- a/src/http_act.c
+++ b/src/http_act.c
@@ -1733,7 +1733,7 @@
case PAT_MATCH_REG:
if (!(rule->arg.http.re = regex_comp(rule->arg.http.str.ptr, 1, 1, err)))
return ACT_RET_PRS_ERR;
- /* fall through */
+ __fallthrough;
case PAT_MATCH_STR:
case PAT_MATCH_BEG:
case PAT_MATCH_END: