Fix the branch predictor's gshare and btb critical path issue
Created by: rosethompson
- Partial replacement of InstrClassX with {JalX, RetX, JumpX, and BranchX}.
- Major cleanup of bp.
- Improved branch predictor graph generation.
- Modified btb forwarding logic to reduce critical path.
- Prep to fix gshare critical path.
- Completed critical path gshare fix.
- Cleanup.
- Possible fix to btb performance issue.