runtime: retype mheap.reclaimIndex as atomic.Uint64

runtime: retype mheap.reclaimIndex as atomic.Uint64

[git-generate]
cd src/runtime
mv export_test.go export.go
GOROOT=$(dirname $(dirname $PWD)) rf '
  add mheap.reclaimIndex \
// reclaimIndex is the page index in allArenas of next page to \
// reclaim. Specifically, it refers to page (i % \
// pagesPerArena) of arena allArenas[i / pagesPerArena]. \
// \
// If this is >= 1<<63, the page reclaimer is done scanning \
// the page marks. \
reclaimIndex_ atomic.Uint64
  ex {
    import "runtime/internal/atomic"

    var t mheap
    var v, w uint64
    var d int64

    t.reclaimIndex -> t.reclaimIndex_.Load()
    t.reclaimIndex = v -> t.reclaimIndex_.Store(v)
    atomic.Load64(&t.reclaimIndex) -> t.reclaimIndex_.Load()
    atomic.LoadAcq64(&t.reclaimIndex) -> t.reclaimIndex_.LoadAcquire()
    atomic.Store64(&t.reclaimIndex, v) -> t.reclaimIndex_.Store(v)
    atomic.StoreRel64(&t.reclaimIndex, v) -> t.reclaimIndex_.StoreRelease(v)
    atomic.Cas64(&t.reclaimIndex, v, w) -> t.reclaimIndex_.CompareAndSwap(v, w)
    atomic.Xchg64(&t.reclaimIndex, v) -> t.reclaimIndex_.Swap(v)
    atomic.Xadd64(&t.reclaimIndex, d) -> t.reclaimIndex_.Add(d)
  }
  rm mheap.reclaimIndex
  mv mheap.reclaimIndex_ mheap.reclaimIndex
'
mv export.go export_test.go

Change-Id: I1d619e3ac032285b5f7eb6c563a5188c8e36d089
Reviewed-on: https://go-review.googlesource.com/c/go/+/356711
Reviewed-by: Austin Clements <austin@google.com>
Trust: Michael Knyszek <mknyszek@google.com>