Introduces a new test API, `includesModule`. The method returns whether
a particular module like "ajax" or "deprecated" is included in the current
jQuery build; it handles the slim build as well. The util was created so that
we don't treat presence of particular APIs to decide whether to run a test as
then if we accidentally remove an API, the tests would still not fail.
Closes gh-5071
Fixes gh-5069
Ref gh-5046
(partially cherry picked from commit fae5fee8b4)
There is a lot of logic in intro.js; now we test four cases:
1. (implicitly, via QUnit tests) A real browser with window being the global
2. Browserify where there are both global & window variables.
3. Node with jsdom where window is passed manually to the jQuery factory.
4. Pure Node with incorrect window passed; jQuery should throw then.
Previously the second & fourth case was not tested and the third was tested
in a way that interfered with the main test environment.
We now also test if in the Browserify case we're not creating a jQuery global
by default.
Fixes gh-2181
Closes gh-2234
