Fix gcc-15.x build

Upstream: https://src.fedoraproject.org/rpms/iftop/c/d098f91f0f590c1cab264bf77851d4018c430d9f?branch=rawhide

Signed-off-by: Bernd Kuhls <bernd@kuhls.net>

diff -up iftop-1.0pre4/cfgfile.h.fargs iftop-1.0pre4/cfgfile.h
--- iftop-1.0pre4/cfgfile.h.fargs	2014-01-05 19:47:53.000000000 +0100
+++ iftop-1.0pre4/cfgfile.h	2025-05-15 18:09:05.849754901 +0200
@@ -13,7 +13,7 @@ typedef struct {
     int value;
 } config_enumeration_type;
 
-int read_config();
+int read_config(char *f, int whinge);
 
 char *config_get_string(const char *directive);
 int config_get_bool(const char *directive);