Specify address via parameter

This allows to decode instructions where the address of the buffer is
not the address of the instruction.

tests/driver.c

@@ -72,7 +72,8 @@ main(int argc, char** argv)
         while (current_off != length)
         {
             size_t remaining = length - current_off;
-            int retval = decode(code + current_off, remaining, mode, &instr);
+            int retval = decode(code + current_off, remaining, mode, 0x1234000,
+                                &instr);
             if (retval < 0)
                 goto fail;
             current_off += retval;