added use_keys argument to array_filter()
forgot introspection changes
fixed test case to pass on other systems than my own
added bitmask variation
Using only two constants to signal use type intent.
Merge branch 'pull-request/287'

Add ability to use array keys with array_filter().
This adds a third (optional) argument to array_filter() that will determine
what gets passed to the callback, the array key, value or both.
The third argument can be one of two constants: ARRAY_FILTER_USE_BOTH or,
ARRAY_FILTER_USE_KEY.