Add decoding of INT and IRET instructions

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

src/libvm/src/mem.rs

@@ -121,8 +121,8 @@ impl<T> MemCursor<T>
             RET => Ok(Inst::Ret),
             PUSH => source!(Push),
             POP => dest!(Pop),
-            INT => { todo!("INT decode") },
+            INT => source_source!(Int),
-            IRET => { todo!("IRET decode") },
+            IRET => Ok(Inst::IRet),
             MOV => dest_source!(Mov),
             HALT => Ok(Inst::Halt),
             NOP => Ok(Inst::Nop),