Uint32 and Uint64 types

[ospencer]

The addition of these types would allow better type safety and code clarity. The Int32 and Int64 types would become the signed variants. This signedness would also affect printing.

Proposed literal suffixes: ul and uL

Last thing to consider would be keeping the unsigned instructions in the Int32 and Int64 libraries / adding signed instructions to the new libraries. I personally think we should remove them—I think a lot of code clarity/type safety would be lost by someone, for example, using the Int32 type but only using unsigned instructions because they were there instead of being required to use the Uint32 type.