Selector: Inline Sizzle into the selector module: 3.x version (#5113)

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

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 main `selector` module can be disabled in favor of `selector-native`
via:

    grunt custom:-selector

For backwards compatibility, the legacy `sizzle` alias is also supported (it
will be dropped in jQuery `4.0.0`):

    grunt custom:-selector

Sizzle tests have been ported to jQuery ones. Ones that are not compatible
with the `selector-native` module are disabled if the regular selector module
is excluded.

Backwards compatibility is still kept for all `Sizzle` utils - they continue to be
available under `jQuery.find` - but the primary implementation is now attached
directly to jQuery.

Some selector utils shared by `selector` & `selector-native` have been
extracted & deduplicated. `jQuery.text` and `jQuery.isXMLDoc` have been
moved to the `core` module.

The commit reduces the gzipped jQuery size by 851 bytes compared to the
`3.x-stable` branch.

Closes gh-5113
Ref gh-4395
Ref gh-4406

1 files changed, 6 insertions, 4 deletions

diff --git a/README.md b/README.md
index c05254e30..f92573666 100644
--- a/README.md
+++ b/README.md
@@ -106,11 +106,13 @@ Some example modules that can be excluded are:
 - **exports/global**: Exclude the attachment of global jQuery variables ($ and jQuery) to the window.
 - **exports/amd**: Exclude the AMD definition.
 
-As a special case, you may also replace Sizzle by using a special flag `grunt custom:-sizzle`.
+As a special case, you may also replace the full jQuery `selector` module by using a special flag `grunt custom:-selector`.
 
-- **sizzle**: The Sizzle selector engine. When this module is excluded, it is replaced by a rudimentary selector engine based on the browser's `querySelectorAll` method that does not support jQuery selector extensions or enhanced semantics. See the [selector-native.js](https://github.com/jquery/jquery/blob/main/src/selector-native.js) file for details.
+- **selector**: The full jQuery selector engine. When this module is excluded, it is replaced by a rudimentary selector engine based on the browser's `querySelectorAll` method that does not support jQuery selector extensions or enhanced semantics. See the [selector-native.js](https://github.com/jquery/jquery/blob/main/src/selector-native.js) file for details.
 
-*Note*: Excluding Sizzle will also exclude all jQuery selector extensions (such as `effects/animatedSelector` and `css/hiddenVisibleSelectors`).
+For backwards compatibility purposes, the name `sizzle` is recognized as the alias for `selector`.
+
+*Note*: Excluding the full `selector` module will also exclude all jQuery selector extensions (such as `effects/animatedSelector` and `css/hiddenVisibleSelectors`).
 
 The build process shows a message for each dependent module it excludes or includes.
 
@@ -167,7 +169,7 @@ There is also a special alias to generate a build with the same configuration as
 grunt custom:slim
 ```
 
-For questions or requests regarding custom builds, please start a thread on the [Developing jQuery Core](https://forum.jquery.com/developing-jquery-core) section of the forum. Due to the combinatorics and custom nature of these builds, they are not regularly tested in jQuery's unit test process. The non-Sizzle selector engine currently does not pass unit tests because it is missing too much essential functionality.
+For questions or requests regarding custom builds, please start a thread on the [Developing jQuery Core](https://forum.jquery.com/developing-jquery-core) section of the forum. Due to the combinatorics and custom nature of these builds, they are not regularly tested in jQuery's unit test process.
 
 Running the Unit Tests
 --------------------------------------