Remove workarounds for the uglify task mishandling banners when used with source maps.

The issue was fixed in grunt-contrib-uglify:
https://github.com/gruntjs/grunt-contrib-uglify/issues/22
No ticket. Restore some parsing tests in core.
Fix #14415. Remove the source map comment in the release script. Close gh-1424.
No ticket. Remove the pre-uglify task form build/tasks/build.js. Fix custom builds.
No ticket. Remove version sniffing from test/unit/support.js, browsers got updated.
Fix #14340. Remove remnants of oldIE from unit tests. Close gh-1425.
No ticket. Remove the unnecessary guard in addGetHookIf. Close gh-1426.

In 1.x if the support test executes before doc ready, it may not be able
to return a result yet. In such a case, we protect ourselves from future
breakages, allowing only for the ones before doc ready.

Since in 2.x lazy support tests attach test elements to docElem, not body,
such a guard is unnecessary.