Pass an alignment mask during heap array allocation,

not an alignment value.

Assert that various entrypoints get an alignment mask.

Get everything uniformly passing an assertion about
dealloating an object with the correct allocation
size; don't actually enable the assertion yet, though.

rdar://16989632

Swift SVN r18550

stdlib/core/HeapBuffer.swift

@@ -49,7 +49,7 @@ func c_malloc_size(heapMemory: UnsafePointer<Void>) -> Int
   deinit {
     Buffer(self)._value.destroy()
   }
-  @final func __getInstanceSizeAndAlignMask() -> (Int,Int) {
+  func __getInstanceSizeAndAlignMask() -> (Int,Int) {
     return Buffer(self)._allocatedSizeAndAlignMask()
   }
 }