Selector: Backport jQuery selection context logic to selector-native

This makes:
```js
$div.find("div > *")
```
no longer matching children of `$div`.

Also, leading combinators now work, e.g.:
```js
$div.find( "> *" );
```
returns children of `$div`.

As a result of that, a number of tests are no longer skipped in the
`selector-native` mode.

Also, rename `rcombinators` to `rleadingCombinator`.

Fixes gh-5185
Closes gh-5186
Ref gh-5085

1 files changed, 26 insertions, 0 deletions

diff --git a/src/selector/createCache.js b/src/selector/createCache.js
new file mode 100644
index 000000000..18e255d0f
--- /dev/null
+++ b/src/selector/createCache.js
@@ -0,0 +1,26 @@
+import jQuery from "../core.js";
+
+/**
+ * Create key-value caches of limited size
+ * @returns {function(string, object)} Returns the Object data after storing it on itself with
+ *	property name the (space-suffixed) string and (if the cache is larger than Expr.cacheLength)
+ *	deleting the oldest entry
+ */
+function createCache() {
+	var keys = [];
+
+	function cache( key, value ) {
+
+		// Use (key + " ") to avoid collision with native prototype properties
+		// (see https://github.com/jquery/sizzle/issues/157)
+		if ( keys.push( key + " " ) > jQuery.expr.cacheLength ) {
+
+			// Only keep the most recent entries
+			delete cache[ keys.shift() ];
+		}
+		return ( cache[ key + " " ] = value );
+	}
+	return cache;
+}
+
+export default createCache;