Add more set-like version constraint operations.

This adds support for union(), as well as checking if constraints are supersets
of or disjoint with one another. These are necessary for some version solver
work I'm doing in pub.

R=rnystrom@google.com

Review URL: https://codereview.chromium.org/1127783002
10 files changed
tree: 95e8b611472bc6bf0d6cadc17c6a1ae69d4476f6
  1. pkgs/