Standby list for dyn bce in potentially infinite loops.

Rationale:
The old code relied on "luck" to revisit basic blocks
after dynamic bce and incorporate all bounds checks
in potentially infinite loops that were "made" finite.
Now that revisiting has been removed completely, keeping
a standby list ensures all candidates are considered.

Change-Id: Ida3cf63be1307be6c2b0258d3e64b163f12be235