eolian: use void to force empty function parameters

We have to use void in a function declaration if we want no function
parameters. Using just empty parenthesis means the function takes an
unspecified number of parameters.

We had it correct for most declarations and this series fixes it for
the rest.

src/lib/eolian/eolian_database.h

@@ -266,8 +266,8 @@ struct _Eolian_Variable
    Eina_Bool is_extern :1;
 };
 
-int database_init();
-int database_shutdown();
+int database_init(void);
+int database_shutdown(void);
 
 char *database_class_to_filename(const char *cname);
 Eina_Bool database_validate(void);