* Generalize tail continues
* Fix DecodeBasicBlock
`Next` and `Branch` would be null, which is not the state expected by
the branch instructions. They end up branching or falling into a block
which is never populated by the `Translator`. This causes an assert to
be fired when building the CFG.
* Clean up Decode overloads
* Do not synchronize when branching into exit block
If we're branching into an exit block, that exit block will tail
continue into another translation which already has a synchronization.
* Remove A32 predicate tail continue
If `block` is not an exit block then the `block.Next` must exist (as
per the last instruction of `block`).
* Throw if decoded 0 blocks
Address gdkchan's feedback
* Rebuild block list instead of setting to null
Address gdkchan's feedback
