[clang] Avoid need for SLocEntryLoaded BitVector (PR #67960)

[Vassil Vassilev via cfe-commits]

================
@@ -474,9 +474,10 @@ static_assert(sizeof(FileInfo) <= sizeof(ExpansionInfo),
 /// SourceManager keeps an array of these objects, and they are uniquely
 /// identified by the FileID datatype.
 class SLocEntry {
-  static constexpr int OffsetBits = 8 * sizeof(SourceLocation::UIntTy) - 1;
+  static constexpr int OffsetBits = 8 * sizeof(SourceLocation::UIntTy) - 2;
   SourceLocation::UIntTy Offset : OffsetBits;
   SourceLocation::UIntTy IsExpansion : 1;
+  SourceLocation::UIntTy Loaded : 1;
----------------
vgvassilev wrote:

```suggestion
  SourceLocation::UIntTy IsLoaded : 1;
```

https://github.com/llvm/llvm-project/pull/67960