[turbofan] Connect non-terminating loops via Terminate.

[turbofan] Connect non-terminating loops via Terminate.

This revives the Terminate operator and removes the weird Always
operator. As a first step we let the ControlReducer connect non
terminating loops via Terminate. The next step will be to change the
graph builder to insert Terminate nodes into every loop.

Committed: https://crrev.com/203438d9bc0866460d15823143ffb2236dd149a5
Cr-Commit-Position: refs/heads/master@{#28259}

[Benedikt Meurer, 2015-05-06 12:28:55]

bmeurer@chromium.org changed reviewers:
+ titzer@chromium.org

[Benedikt Meurer, 2015-05-06 12:28:55]

Hey Ben,

Reviving good old Terminate and remove the lovely Always...
Please take a look.

Thanks,
Benedikt

[titzer, 2015-05-06 12:31:48]

On 2015/05/06 12:28:55, Benedikt Meurer wrote:
> Hey Ben,
> 
> Reviving good old Terminate and remove the lovely Always...
> Please take a look.
> 
> Thanks,
> Benedikt

LGTM

[Benedikt Meurer, 2015-05-06 12:32:05]

The CQ bit was checked by bmeurer@chromium.org

[commit-bot: I haz the power, 2015-05-06 12:32:09]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1123213002/1

[commit-bot: I haz the power, 2015-05-06 12:51:45]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-06 12:51:57]

Patchset 1 (id:??) landed as
https://crrev.com/203438d9bc0866460d15823143ffb2236dd149a5
Cr-Commit-Position: refs/heads/master@{#28259}