TableGen support for Intrinsics with multiple outputs

From class Intrinsic defined in Intrinsics.td [1], yes, Intrinsic allows multiple return types.
Seems no other backend ever complain this, so either we change the class Intrinsic definition
or we fix the TableGen.

Jakob, sorry for interrupt. What do you think the better way to deal with this?

Thanks.

[1] https://github.com/llvm-mirror/llvm/blob/master/include/llvm/IR/Intrinsics.td

​Regards,
chenwj​