remove code that is no longer used:

- `cacheoveride`
- `Bitmap.SetCount()`

bitmap.go

@@ -16,8 +16,6 @@ type Bitmap struct {
 
 	// Attributes associated with the bitmap.
 	Attrs map[string]interface{}
-
-	cacheoveride uint64
 }
 
 // NewBitmap returns a new instance of Bitmap.
@@ -191,10 +189,6 @@ func (b *Bitmap) DecrementCount(i uint64) {
 		}
 	}
 }
-func (b *Bitmap) SetCount(i uint64, count uint64) {
-	seg := b.segment(i / SliceWidth)
-	seg.n = count
-}
 
 // Count returns the number of set bits in the bitmap.
 func (b *Bitmap) Count() uint64 {

fragment.go

@@ -337,10 +337,8 @@ func (f *Fragment) bitmap(bitmapID uint64, checkBitmapCache bool, updateBitmapCa
 			slice:    f.slice,
 			writable: false,
 		}},
-		cacheoveride: 0,
 	}
 	bm.InvalidateCount()
-	bm.cacheoveride = bm.Count()
 
 	if updateBitmapCache {
 		f.bitmapCache.Add(bitmapID, bm)