fix some edge cases related to function params and methods that references `this`

This fixes most of the false positives on jQuery source code (2 pending: `value` and `callbackName`).

Implementation is still *brittle*, specially since user might change the execution context with `apply`, `call` or depending on how he calls the method (eg. callback is an Identifier and/or MemberExpression).

static analysis is not easy and full of edge cases..