[MINOR] acl: add REQ_CONTENT to the list of default acls

With content inspection, checking the presence of data in the
request buffer is very important. It's getting boring to always
add such an ACL, so let's add it by default.
diff --git a/src/acl.c b/src/acl.c
index 6385c6f..983c0c5 100644
--- a/src/acl.c
+++ b/src/acl.c
@@ -758,6 +758,7 @@
 	{ .name = "HTTP_URL_SLASH", .expr = {"url_beg","/",""}},
 	{ .name = "HTTP_URL_STAR",  .expr = {"url","*",""}},
 	{ .name = "HTTP_CONTENT",   .expr = {"hdr_val(content-length)","gt","0",""}},
+	{ .name = "REQ_CONTENT",    .expr = {"req_len","gt","0",""}},
 	{ .name = NULL, .expr = {""}}
 };