fix for global_name 'compile_exor' is not defined

```
Traceback (most recent call last):
  File "runtests.py", line 16, in <module>
    code = cllcompiler.assemble(cllcompiler.compile_stmt(ast))
  File "/Users/aeufemio/projects/ethereum/compiler/cllcompiler.py", line 165, in compile_stmt
    o.extend(compile_stmt(s,varhash,lc))
  File "/Users/aeufemio/projects/ethereum/compiler/cllcompiler.py", line 151, in compile_stmt
    rexp = compile_expr(stmt[2],varhash)
  File "/Users/aeufemio/projects/ethereum/compiler/cllcompiler.py", line 109, in compile_expr
    return compile_exor(expr[2],varhash) + pseudoarrays[expr[1]]
NameError: global name 'compile_exor' is not defined

```