struct Init -> class Init

Rename struct Init to class Init for consistency and in preparation
for making Init a FoldingSetNode.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@135097 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/utils/TableGen/SetTheory.h b/utils/TableGen/SetTheory.h
index e37a76e..6e8313b 100644
--- a/utils/TableGen/SetTheory.h
+++ b/utils/TableGen/SetTheory.h
@@ -55,7 +55,7 @@
 namespace llvm {
 
 class DagInit;
-struct Init;
+class Init;
 class Record;
 class RecordKeeper;