GitLab

1. Stack overflow fixed by making dataflow monad strict in the state.
2. Out of memory fixed by "forgetting" lastoutfacts in the dataflow monad
   where we should. We were creating an unnecessarily long list that grew
   exponentially...

Among others:
- Fixed Stg->C-- translation of let-no-escapes -- it's important to use the
  right continuation...
- Fixed infinite recursion in X86 backend (shortcutJump mishandled infinite loops)
- Fixed yet another wrong calling convention -- primops take args only in vanilla regs,
  but they may return results on the stack!
- Removed StackInfo from LGraph and Block -- now in LastCall and CmmZ
- Updated avail-variable and liveness code

The interesting examples talk about our story with heap checks in
case alternatives and our story with the case scrutinee as a Boolean.

o The linear-scan register allocator sometimes allocated a block
  before allocating one of its predecessors, which could lead
  to inconsistent allocations. Now, we allocate a block only
  if a predecessor has set the "incoming" assignments for the block
  (or if it's the procedure's entry block).
o Also commented out some tracing code on the new codegen path.

Before: building a closure that would build an SRT given the top-level
SRT. It was somewhat difficult to understand the control flow, and it
may have had held onto some data structures long after they should be dead.
Now, I just bundle the info we need about CAFs along with the procedure
and directly call a new top-level function to build the SRTs later.