Bug 987163 - Mirror the TypedArray ClassSpec between instance and proto JSClasses. r=luke

The Xray code expects to be able to find the ClassSpec via the JSClass of either
instances or standard prototypes. So in the case where these two objects have
different JSClasses, we need to put the information on both.
Bug 987163 - Convert from |switch| statements to |if| statements. r=gabor

I realized that the switches are going to be cumbersome for Array stuff, because
we'll have to enumerate each kind of TypedArray as a separate case: statement.
Let's just use |if| so that we can call a helper.
Bug 987163 - Fix some squelched OOMs. r=gabor
Bug 987163 - Drop special COW support for TypedArrays. r=gabor

From now on, if someone wants to expose a TypedArray to content, they should
use Cu.cloneInto.
Bug 987163 - Test fixups. r=gabor
Bug 987163 - Implement Xrays for TypedArrays. r=gabor