[Dominators] Clean up GenericDomTree.h. NFC.
[Dominators] Clean up GenericDomTree.h. NFC.

Summary:
This patch cleans up GenericDomTree.h by:

- removing unnecessary <NodeT> in DomTreeNodeBase
- removing unnecessary std::move on bools
- changing type of DFSNumIn/DFSNumOut from int to unsigned (since the members were used as unsigned anyway)

The changes don't affect behavior -- everything works as before.

Reviewers: sanjoy, dberlin, chandlerc

Reviewed By: dberlin

Subscribers: davide, llvm-commits

Differential Revision: https://reviews.llvm.org/D34229

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@305710 91177308-0d34-0410-b5e6-96231b3b80d8

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