Lexical analyzer prints warning if unknown tokens
Lexical analyzer prints warning if unknown tokens

fixes:
```
Traceback (most recent call last):
  File "/Users/cunnie/bin/VMTranslator.py", line 374, in <module>
    writecode(x)
  File "/Users/cunnie/bin/VMTranslator.py", line 341, in writecode
    sys.exit(cmd_name + " I can't recognize these tokens: " + tokens)
TypeError: cannot concatenate 'str' and 'list' objects
```

cunnie/bin,cunnie/bin,cunnie/bin,cunnie/bin,cunnie/bin,cunnie/bin,cunnie/bin