Selector: Inline Sizzle into the selector module

This commit removes Sizzle from jQuery, inlining its code & removing obsolete
workarounds where applicable.

The selector-native module has been removed. Further work on the selector
module may decrease the size enough that it will no longer be necessary. If
it turns out it's still useful, we'll reinstate it but the code will look
different anyway as we'll want to share as much code as possible with
the existing selector module.

The Sizzle AUTHORS.txt file has been merged with the jQuery one - people are
sorted by their first contributions to either of the two repositories.

The commit reduces the gzipped jQuery size by 1460 bytes compared to master.

Closes gh-4395

.mailmap

@@ -4,6 +4,8 @@ Alexander Farkas <info@corrupt-system.de>
 Alexander Farkas <info@corrupt-system.de> <a.farkas.pm@googlemail.com>
 Alexis Abril <me@alexisabril.com> <alexis.abril@gmail.com>
 Andrew E Monat <amonat@gmail.com>
+Andrey Meshkov <ay.meshkov@gmail.com>
+Andrey Meshkov <ay.meshkov@gmail.com> <am@adguard.com>
 Anton Matzneller <obhvsbypqghgc@gmail.com>
 Anton Matzneller <obhvsbypqghgc@gmail.com> <haskell_noob-github@yahoo.de>
 Batiste Bieler <batiste.bieler@gmail.com>
@@ -13,6 +15,8 @@ Carl Danley <carldanley@gmail.com>
 Carl Fürstenberg <azatoth@gmail.com>
 Carl Fürstenberg <azatoth@gmail.com> <carl@excito.com>
 Charles McNulty <cmcnulty@kznf.com>
+Chris Rebert <github@rebertia.com>
+Chris Rebert <github@rebertia.com> <code@rebertia.com>
 Christopher Jones <chris@cjqed.com> cjqed <christopherjonesqed@gmail.com>
 Colin Snover <github.com@zetafleet.com> <colin@alpha.zetafleet.com>
 Corey Frang <gnarf37@gmail.com> <gnarf@gnarf.net>
@@ -52,6 +56,8 @@ Josh Varner <josh.varner@gmail.com> <josh.varner@gmail.com>
 Julian Aubourg <aubourg.julian@gmail.com>
 Julian Aubourg <aubourg.julian@gmail.com> <j@ubourg.net>
 Julian Aubourg <aubourg.julian@gmail.com> <Julian@.(none)>
+John Firebaugh <john_firebaugh@bigfix.com>
+John Firebaugh <john_firebaugh@bigfix.com> <john_firebaugh@us.ibm.com>
 Jörn Zaefferer <joern.zaefferer@gmail.com>
 Jörn Zaefferer <joern.zaefferer@gmail.com> <joern.zaefferer@googlemail.com>
 Jörn Zaefferer <joern.zaefferer@gmail.com> <JZA@.(none)>