Add option to ignore deprecation inside a deprecated context

[RebeccaStevens]

For example, this would not cause anything to be flagged:

/**
 * @deprecated
 */
function foo() {
  call_to_deprecated_function();
}

But if @deprecated is removed from foo, then call_to_deprecated_function is flagged.

If I get some free time I might look into making a PR for this.