chapter336 [M1], Adding uint256 operator * / %

Supports multiplication, division, and remainder for uint256.

uint256 ui1(12345678);
uint256 ui2("0x00002046b1c7938971a6089c7105fc15907b8f27ac8dfea");

uint256 r = ui2 * ui1;
::fprintf(stdout, "uint256 mul 0x%s\n", r.ToString().c_str());
uint256 r = ui2 / ui1;
::fprintf(stdout, "uint256 div 0x%s\n", u1.ToString().c_str());
uint256 r = ui2 % ui1;
::fprintf(stdout, "uint256 rem 0x%s\n", u1.ToString().c_str());