Fixes for relvals

Fixes/workarounds for two ROOT6 limitations that are causing all relvals to fail.  Note that even with these fixes, the relvals will still fail for other reasons.

1) Root 6 cannot yet handle unnamed enums properly. Replace
typedef enum { Unknown=-1, Obsolete, Tag, TagInGT, ChildTag, ChildTagInGT } ScopeType;
with
enum ScopeType { Unknown=-1, Obsolete, Tag, TagInGT, ChildTag, ChildTagInGT };
This change can be permanent.

2) Root 6 cannot yet handle user defined attributes on "field name=" lines in xml selection files.
Comment out exceptions that would otherwise be thrown due to this limitation.
This change will be reverted once ROOT fixes this.