Save the closure return data type for further use.

include/ph7int.h

@@ -1001,6 +1001,7 @@ struct ph7_vm_func {
 	SySet aByteCode;     /* Compiled function body */
 	SySet aClosureEnv;   /* Closure environment (ph7_vm_func_closure_env instace) */
 	sxi32 iFlags;        /* VM function configuration */
+	sxu32 nType;         /* Return data type expected by this function */
 	SyString sSignature; /* Function signature used to implement function overloading
 						  * (Refer to the official documentation for more information
 						  *  on this powerfull feature)