Int - Int-Uint interoperability (#736)

Adds `Int::div_uint` and `Int::mul_uint`

Author: erik-3milabs

src/int.rs

@@ -18,10 +18,12 @@ mod bit_or;
 mod bit_xor;
 mod cmp;
 mod div;
+mod div_uint;
 mod encoding;
 mod from;
 mod inv_mod;
 mod mul;
+mod mul_uint;
 mod neg;
 mod resize;
 mod shl;