swift234

[libdispatch-data-fixes] Appending UnsafeBufferPointers to data is unsafe

    * The buffer-pointer based init methods were passing the dispatch
    data default destructor in such a way that the
    @convention(block)-ness was lost. This leads to a thunk being passed
    to dispatch instead of NULL. Subsequently, dispatch would reference
    rather than copy the provided data.

    Fixes:
	SR-2050 (<rdar://problem/27293973>)