Ask geographicalId() directly from TransientTrackingRecHit.

CPU performance improvement, results stayed the same.
Require triplets to share two hits before inserting them to list of triplet pairs.

CPU performance improvement, results stay the same.
Use k-d tree for search of compatible triplets.

CPU performance improvement, results stay the same.
Identify the (non-)shared hits of triplets already when requiring two hits being shared.

CPU performance improvement, results stay the same.
Removed one repeated std::vector allocation+copy in mySort().

CPU performance improvement, results stay the same.
Removed the rest of relevant TransientTrackingRecHit::hit() calls.

CPU performance improvement, results stay the same.
Change pow(x, 2.) to x*x

pow() is supposedly (much) slower, although in the big picture the
effect on timing is very small. Physics results should stay the same.
Merge pull request #784 from makortel/quadrupletseeds62xslhc

Performance improvement in quadruplet seeding (62X_SLHC)