Added a program init function

src/errors/Common.go

@@ -17,6 +17,7 @@ var (
 	MissingExpression          = &Base{"Missing expression"}
 	MissingGroupStart          = &Base{"Missing '('"}
 	MissingGroupEnd            = &Base{"Missing ')'"}
+	MissingInitFunction        = &Base{"Missing init function"}
 	MissingMainFunction        = &Base{"Missing main function"}
 	MissingOperand             = &Base{"Missing operand"}
 	MissingParameter           = &Base{"Missing parameter"}