Fix BoundOrAssignedEvalOrArgumentsCheck to ignore equality expressions.

An easy way for a JS function to check how many arguments it has is
  arguments.length === x

The old check thinks the above is a modification. We can change the check to
  not fire if it has an ancestor that is an equality expression.

Unfortunately, the new check won't generate a violation for the following:
  (arguments = 1) === 1

I'm hoping the latter won't occur too much, while the former is a common
  pattern and false positives are annoying. There might be a way to catch
  the second case while ignoring the first, but I'm not familiar enough with
  the generated AST.