exif: Eliminated an offset constant. Just used for tests.

- Will simplify fixing the header issues we have. It's relative, any way
  (won't be affected by the imminent changes to the header).

exif.go

@@ -17,10 +17,6 @@ const (
     // offsets are relative to.
     ExifAddressableAreaStart = uint32(0x6)
 
-    // RootIfdExifOffset is the relative offset of the first IFD in the block
-    // of EXIF data.
-    RootIfdExifOffset = uint32(0x0008)
-
     // ExifDefaultFirstIfdOffset is essentially the number of bytes in addition
     // to `ExifAddressableAreaStart` that you have to move in order to escape
     // the rest of the header and get to the earliest point where we can put

exif_test.go

@@ -234,7 +234,7 @@ func TestCollect(t *testing.T) {
     tree := index.Tree
     lookup := index.Lookup
 
-    if rootIfd.Offset != RootIfdExifOffset {
+    if rootIfd.Offset != uint32(0x0008) {
         t.Fatalf("Root-IFD not correct: (0x%04d).", rootIfd.Offset)
     } else if rootIfd.Id != 0 {
         t.Fatalf("Root-IFD does not have the right ID: (%d)", rootIfd.Id)

ifd_builder_encode_test.go

@@ -537,7 +537,7 @@ func validateExifSimpleTestIb(exifData []byte, t *testing.T) {
         t.Fatalf("IFD name not correct.")
     } else if ifd.Index != 0 {
         t.Fatalf("IFD index not zero: (%d)", ifd.Index)
-    } else if ifd.Offset != RootIfdExifOffset {
+    } else if ifd.Offset != uint32(0x0008) {
         t.Fatalf("IFD offset not correct.")
     } else if len(ifd.Entries) != 4 {
         t.Fatalf("IFD number of entries not correct: (%d)", len(ifd.Entries))