evdev: Import support for touch-tracking.

Touch tracking is a process of assignment of unique trackingID to each
initiated contact on the surface. Keeping the trackingIDs persistent
across multitouch reports requires solving of so called Euclidian
Bipartite Matching problem.

This commit imports EBM-solver implementation based on Dinitz-Kronrod
algorithm to find minimum cost matching between contacts listed in two
consecutive reports.

Obtained from: OpenBSD
MFC after: 2 weeks