Add fuzzy type matching for operands to Instruction#encode/#initialize

[postmodern]

In order to support implicit typecasting of operands, the operand classes should support some kind of fuzzy type matching, if a specific size or type has not been specified. This would allow using unsized immediate or memory operands where a imm32 or mem32 operand is required.

This would also reduce the need for having to specify byte(...) or qword(...) all of the type to specify an operands explicit size.

Example

mov eax, 0xff

In the above example, 0xff will be coerced to Immediate.new(0xff, size: 1) since 0xff is 8 bits, but the mov instruction only supports mov reg32, imm32 and mov reg8, imm8. Thus we should treat 0xff as an unsized Immediate operand and try to fuzzy match it against imm32.

[postmodern]

This can finally be closed.