liblas test

Add a simple (bad) test for liblas. Per
https://github.com/Homebrew/homebrew/wiki/Formula-Cookbook#add-a-test-to-the-formula,
a `foo --version` style test is inferior to a functional test, but since
finding or grabbing or creating a lasfile is non-trivial, it is arguable
that a `--version` test is ok here (or at least better than no test).

Users can install `--with-test` to run liblas's internal tests after
building for a more complete test of the suite.