Standardize the values for invalid and data opcodes (#261)

* Standardize the value for an invalid opcode
>
> This makes it so that all arches share the same value for an invalid opcode, so platform-specific logic isn't needed for checking whether instructions are valid.
Also updated dependencies

* OPCODE_DATA too

objdiff-core/src/arch/mod.rs

@@ -41,6 +41,9 @@ pub mod superh;
 #[cfg(feature = "x86")]
 pub mod x86;
 
+pub const OPCODE_INVALID: u16 = u16::MAX;
+pub const OPCODE_DATA: u16 = u16::MAX - 1;
+
 /// Represents the type of data associated with an instruction
 #[derive(PartialEq)]
 pub enum DataType {