Remove some compiler warnings in calculator test (needed since Linux Mint 19)

diff --git a/tests/cal.y b/tests/cal.y
index 637cb82..e73a2b6 100644 (file)
--- a/tests/cal.y
+++ b/tests/cal.y
@@ -2,6 +2,9 @@
 #include <ctype.h>
 #include <stdio.h>
 #define YYSTYPE double
+
+int yylex(void);
+void yyerror(char *s);
 %}
 %token NUM
 
@@ -34,7 +37,7 @@ int main()
   yyparse();
 }
 
-yyerror(char * s)
+void yyerror(char *s)
 {
   printf("%s\n", s);
   exit(1);