codeql static analysis warnings

[jimying]

These codeql warnings maybe need fix

Multiplication result converted to larger type	A multiplication result that is converted to a larger type can be a sign that the result can overflow the type converted from.	warning	Multiplication result may overflow 'int' before it is converted to 'slimb_t'.	/libbf.c	3636	20	3636	47
Multiplication result converted to larger type	A multiplication result that is converted to a larger type can be a sign that the result can overflow the type converted from.	warning	Multiplication result may overflow 'unsigned long' before it is converted to 'unsigned __int128'.	/libbf.c	1962	14	1962	18
Multiplication result converted to larger type	A multiplication result that is converted to a larger type can be a sign that the result can overflow the type converted from.	warning	Multiplication result may overflow 'int' before it is converted to 'size_t'.	/quickjs.c	1410	43	1410	62