Revert "Formal parameter names can be the same as function name. Fixes g...

...h-1928"

@rwaldron @caitp For additional context, see [my comment from yesterday morning](https://github.com/jshint/jshint/pull/2026#issuecomment-67017936)

Commit message:

> This reverts commit 248e40bc39c1110ca7eb1d9799804ce005b9d2f5.
> 
> The issue which motivated this change related to the modification of the environment record of ES6 concise methods. That issue was addressed in a more comprehensive and concise manner via commit b95f669dbb62158355c0fb6a7638c7ccf036dc93 and verified with an equivalent unit test.