Remove CPointer<T>, it was almost equivalent to UnsafePointer<T>, but implemented pointer arithmetic.  Enhanced UnsafePointer<T> to do pointer arithmetic.
Remove CPointer<T>, it was almost equivalent to UnsafePointer<T>, but
implemented pointer arithmetic.  Enhanced UnsafePointer<T> to do pointer
arithmetic.

Also: update Clang importer to import T* as UsafePointer<T>, fix standard
library fallout.


Swift SVN r5616

apple/swift-corelibs-foundation,apple/swift-corelibs-foundation,apple/swift-corelibs-foundation,apple/swift-corelibs-foundation,apple/swift-corelibs-foundation