Fixed issue with pointer arith.

As mentioned in the other PR I closed, This uses a blacklist because the whitelist would need to include < > <= >= && || which take up even more space. Hopefully I didn't miss any operators.

I also learnt how to squash commits which is handy :).
I now prefer writing this as a separate function. Sorry about that.
It needs to be a white list because the number of operators allowed for pointers is fewer than banned ones. For example this expression doesn't cover >>.