Changed `isEqualTo:` (AppleScript support) to `isEqual:` (NSObject)

The method `isEqualTo:` is part of the scripting support API (for computing `NSWhoseSpecifier`s specifically), the proper selector would thus be `isEqual:`.

Reference: https://developer.apple.com/library/mac/documentation/cocoa/reference/foundation/Protocols/NSComparisonMethods_Protocol/Reference/Reference.html#//apple_ref/occ/instm/NSObject/isEqualTo: