This replaces the old JSUnit test harness with an embedded copy of
Jasmine [1], which makes writing tests less of a pain, includes more
handy test facilities, and produces better output.

jasmine.js is a copy of upstream Jasmine 2.5.2. minijasmine.js contains
code for starting up Jasmine, adapting it to the GJS environment, and
producing TAP output. minijasmine.cpp makes an executable which loads the
preceding two files from the unit test GResource.

All the tests in installed-tests/js are converted to use Jasmine's
describe()/it() style. Quite often this allows simplifying them since
Jasmine has features like array and object equality, spies, and clock
ticks.

[1] https://jasmine.github.io/2.5/introduction.html

https://bugzilla.gnome.org/show_bug.cgi?id=775444