[LLVM-C] Move LLVMDISubrangeTypeMetadataKind to end of its enum

Inserting a new enum constant in the middle of the enum breaks the ABI for
that enum. Commit e298fc2 introduced this issue, which was revealed because
the OCaml binding tests failed.

Author: alan-j-hu

llvm/include/llvm-c/DebugInfo.h

@@ -172,7 +172,6 @@ enum {
   LLVMDIEnumeratorMetadataKind,
   LLVMDIBasicTypeMetadataKind,
   LLVMDIDerivedTypeMetadataKind,
-  LLVMDISubrangeTypeMetadataKind,
   LLVMDICompositeTypeMetadataKind,
   LLVMDISubroutineTypeMetadataKind,
   LLVMDIFileMetadataKind,
@@ -196,6 +195,7 @@ enum {
   LLVMDIGenericSubrangeMetadataKind,
   LLVMDIArgListMetadataKind,
   LLVMDIAssignIDMetadataKind,
+  LLVMDISubrangeTypeMetadataKind,
 };
 typedef unsigned LLVMMetadataKind;