The CTLayout constructor called CFRetain() on the associated
CTTextStyle's attribute directory (a CFMutableDictionaryRef) and the
destructor then called CFRelease() on it, even if there was no
guarantee it was still the same CTTextStyle. And in the scenario that
caused this crash, AquaSalGraphics::SetFont() had in fact deleted the
original CTTextStyle and created a new one.

It seems to me that these CFRetain() and CFRelease() calls are not
necessary.

Change-Id: I18e03965dd05d450955353f8c48f111c19a069e3