fix c23 unprototyped function, patch from upstream
https://code.blinkace.com/pdw/iftop/-/commit/67b685c8442528bb30485f6efa212f599ef19baf.patch
--- a/cfgfile.h
+++ b/cfgfile.h
@@ -13,7 +13,7 @@ typedef struct {
     int value;
 } config_enumeration_type;
 
-int read_config();
+int read_config(char *file, int whinge_on_error);
 
 char *config_get_string(const char *directive);
 int config_get_bool(const char *directive);