Except for OpConstant and OpSpecConstant, all other literal number
operands are indeed unsigned integers. So,
* Rename all *LITERAL_NUMBER* operand types to *LITERAL_INTEGER*.
* Expect unsigned integers for *LITERAL_INTEGER* operands.
* Keep MULITPLE_WORD_LITERAL untouched since it is only used by
OpConstant and OpSpecConstant.
And we want to provide the capability to specify floating-point
numbers after !<integer> in the alternate parsing mode. So,
OPTIONAL_LITERAL_NUMBER is reserved for OPTIONAL_CIV.
