[Meta] Drop IE8 support

After much discussion Drupal 8 will not support IE8: #1787012-139: [policy, no patch] Write D8 JS against ECMAScript 5. Prevent errors with feature detection (drop IE8 support).

This issue is about listing all IE8-related issues and tracking the progress of IE8 removal. Everything that will be undone here should be ported to the ie8 module to make sure it's possible for contrib to add back the compatibility.

• #1465948: [meta] Drop some IE8 coddling from Drupal core
• #1787146: Make IE8 behave as no-js (do not run any Drupal JavaScript on IE8)
• #1787012: [policy, no patch] Write D8 JS against ECMAScript 5. Prevent errors with feature detection (drop IE8 support)
• #1030090: Document our browser support list
• #1974340: Update to jQuery 2
• #1649780: Remove first/last/odd/even classes in favor of CSS3 pseudo selectors
• #1645494: Allow core themes to display single-column on IE8: do not compensate for lack of media query support
• #1515734: form.js' 'formUpdated' behavior is slow because it binds to each element rather than delegating
• #1993334: Add HTML5shiv to Stable and Classy only

This issue started as a javascript-focused one but CSS can take advantage of it as well.