MEDIUM: proxy: remove acl_requires and just keep a flag "http_needed"

Proxy's acl_requires was a copy of all bits taken from ACLs, but we'll
get rid of ACL flags and only rely on sample fetches soon. The proxy's
acl_requires was only used to allocate an HTTP context when needed, and
was even forced in HTTP mode. So better have a flag which exactly says
what it's supposed to be used for.
diff --git a/src/cfgparse.c b/src/cfgparse.c
index 6b27c24..e277b12 100644
--- a/src/cfgparse.c
+++ b/src/cfgparse.c
@@ -3040,8 +3040,7 @@
 		}
 
 		/* check if we need to allocate an hdr_idx struct for HTTP parsing */
-		if (expr->fetch->use & SMP_USE_HTTP_ANY)
-			curproxy->acl_requires |= ACL_USE_L7_ANY;
+		curproxy->http_needed |= !!(expr->fetch->use & SMP_USE_HTTP_ANY);
 
 		if (strcmp(args[myidx], "table") == 0) {
 			myidx++;
@@ -6044,7 +6043,7 @@
 			break;
 
 		case PR_MODE_HTTP:
-			curproxy->acl_requires |= ACL_USE_L7_ANY;
+			curproxy->http_needed = 1;
 			break;
 		}