* Mutations of slices of data should preserve relative indexing as well as cow semantics of slices
* Ensure hashes of ranges are uniform to the expected hash for Data
* Correct a few mistakes in the slice mutation tests
* Update sequence initializations to avoid directly calling mutableCopy which prevents slice offset mismatches
* Avoid invalid index slices in creating mirrors
* Restore the original Data description
* Resetting a slice region should expand the slice to the maximum of the region (not a out of bounds index of the backing buffer)
* Remove stray comment and use a stack buffer for sequence appending
* Return false when allocations fail in _resizeConditionalAllocationBuffer (not yet in use)
* Enumeration of regions of a slice should be limited to the slice range in the case of custom backing (e.g. dispatch_data_t)
* adjust assertion warnings for data indexes that are negative
This avoids indirection by making calls directly to the C implementations which prevents potentials of mismatched intent or changes of calling convention of @_silgen. The added benefit is that all of the shims in this case are no longer visible symbols (anyone using them was not authorized out side of the Foundation overlay). Also the callout methods in the headers now all share similar naming shcemes for easier refactoring and searching in the style of __NS<class><action> style. The previous compiled C/Objective-C source files were built with MRR the new headers MUST be ARC by Swift import rules.
The one caveat is that certain functions MUST avoid the bridge case (since they are part of the bridging code-paths and that would incur a recursive potential) which have the types erased up to NSObject * via the macro NS_NON_BRIDGED.
The remaining @_silgen declarations are either swift functions exposed externally to the rest of Swift’s runtime or are included in NSNumber.gyb which the Foundation team has other plans for removing those @_silgen functions at a later date and Data.swift has one external function left with @_silgen which is blocked by a bug in the compiler which seems to improperly import that particular method as an inline c function.
