[Dominators] Clean up typedefs in GenericDomTreeConstruction. NFC.

Summary: This patch cleans up GenericDomTreeConstruction by replacing typedefs with usings and replaces `typename GraphT::NodeRef` with `NodePtr` to make the file more readable.

Reviewers: sanjoy, dberlin, chandlerc

Reviewed By: dberlin

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D34254

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@305715 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed