Moved a bunch of methods out of the jQuery-specific Sizzle code into more-appropriate files, in jQuery itself.

src/core.js

@@ -222,7 +222,7 @@ jQuery.fn = jQuery.prototype = {
 	},
 
 	is: function( selector ) {
-		return !!selector && jQuery.multiFilter( selector, this ).length > 0;
+		return !!selector && jQuery.filter( selector, this ).length > 0;
 	},
 
 	// For internal use only.

src/css.js

@@ -197,3 +197,19 @@ jQuery.extend({
 		}
 	}
 });
+
+if ( jQuery.expr && jQuery.expr.filters ) {
+	jQuery.expr.filters.hidden = function(elem){
+		var width = elem.offsetWidth, height = elem.offsetHeight,
+			 force = /^tr$/i.test( elem.nodeName ); // ticket #4512
+		return ( width === 0 && height === 0 && !force ) ?
+			true :
+				( width !== 0 && height !== 0 && !force ) ?
+					false :
+						!!( jQuery.curCSS(elem, "display") === "none" );
+	};
+
+	jQuery.expr.filters.visible = function(elem){
+		return !jQuery.expr.filters.hidden(elem);
+	};
+}

src/fx.js

@@ -420,3 +420,11 @@ jQuery.extend( jQuery.fx, {
 		}
 	}
 });
+
+if ( jQuery.expr && jQuery.expr.filters ) {
+	jQuery.expr.filters.animated = function(elem){
+		return jQuery.grep(jQuery.timers, function(fn){
+			return elem === fn.elem;
+		}).length;
+	};
+}

src/manipulation.js

@@ -333,7 +333,7 @@ jQuery.each({
 jQuery.each({
 	// keepData is for internal use only--do not document
 	remove: function( selector, keepData ) {
-		if ( !selector || jQuery.multiFilter( selector, [ this ] ).length ) {
+		if ( !selector || jQuery.filter( selector, [ this ] ).length ) {
 			if ( !keepData && this.nodeType === 1 ) {
 				cleanData( this.getElementsByTagName("*") );
 				cleanData( [ this ] );

src/selector.js

@@ -998,67 +998,6 @@ var posProcess = function(selector, context){
 jQuery.find = Sizzle;
 jQuery.expr = Sizzle.selectors;
 jQuery.expr[":"] = jQuery.expr.filters;
-
-Sizzle.selectors.filters.hidden = function(elem){
-	var width = elem.offsetWidth, height = elem.offsetHeight,
-		 force = /^tr$/i.test( elem.nodeName ); // ticket #4512
-	return ( width === 0 && height === 0 && !force ) ?
-		true :
-			( width !== 0 && height !== 0 && !force ) ?
-				false :
-					!!( jQuery.curCSS(elem, "display") === "none" );
-};
-
-Sizzle.selectors.filters.visible = function(elem){
-	return !Sizzle.selectors.filters.hidden(elem);
-};
-
-Sizzle.selectors.filters.animated = function(elem){
-	return jQuery.grep(jQuery.timers, function(fn){
-		return elem === fn.elem;
-	}).length;
-};
-
-jQuery.filter = jQuery.multiFilter = function( expr, elems, not ) {
-	if ( not ) {
-		expr = ":not(" + expr + ")";
-	}
-
-	return Sizzle.matches(expr, elems);
-};
-
-jQuery.dir = function( elem, dir ){
-	var matched = [], cur = elem[dir];
-	while ( cur && cur != document ) {
-		if ( cur.nodeType == 1 )
-			matched.push( cur );
-		cur = cur[dir];
-	}
-	return matched;
-};
-
-jQuery.nth = function(cur, result, dir, elem){
-	result = result || 1;
-	var num = 0;
-
-	for ( ; cur; cur = cur[dir] )
-		if ( cur.nodeType == 1 && ++num == result )
-			break;
-
-	return cur;
-};
-
-jQuery.sibling = function(n, elem){
-	var r = [];
-
-	for ( ; n; n = n.nextSibling ) {
-		if ( n.nodeType == 1 && n != elem )
-			r.push( n );
-	}
-
-	return r;
-};
-
 jQuery.unique = Sizzle.uniqueSort;
 
 return;

src/traversing.js

@@ -10,8 +10,8 @@ var winnow = function( elements, qualifier, keep ) {
 	} else if( typeof qualifier === "string" ) {
 		var filtered = jQuery.grep(elements, function(elem) { return elem.nodeType === 1 });
 
-		if(isSimple.test( qualifier )) return jQuery.multiFilter(qualifier, filtered, !keep);
+		if(isSimple.test( qualifier )) return jQuery.filter(qualifier, filtered, !keep);
-		else qualifier = jQuery.multiFilter( qualifier, elements );
+		else qualifier = jQuery.filter( qualifier, elements );
 	}
 
 	return jQuery.grep(elements, function(elem, i) {
@@ -128,7 +128,7 @@ jQuery.each({
 		var ret = jQuery.map( this, fn );
 
 		if ( selector && typeof selector === "string" ) {
-			ret = jQuery.multiFilter( selector, ret );
+			ret = jQuery.filter( selector, ret );
 		}
 
 		ret = this.length > 1 ? jQuery.unique( ret ) : ret;
@@ -140,3 +140,49 @@ jQuery.each({
 		return this.pushStack( ret, name, selector );
 	};
 });
+
+jQuery.extend({
+	filter: function( expr, elems, not ) {
+		if ( not ) {
+			expr = ":not(" + expr + ")";
+		}
+
+		return jQuery.find.matches(expr, elems);
+	},
+	
+	dir: function( elem, dir ) {
+		var matched = [], cur = elem[dir];
+		while ( cur && cur.nodeType !== 9 ) {
+			if ( cur.nodeType === 1 ) {
+				matched.push( cur );
+			}
+			cur = cur[dir];
+		}
+		return matched;
+	},
+
+	nth: function( cur, result, dir, elem ) {
+		result = result || 1;
+		var num = 0;
+
+		for ( ; cur; cur = cur[dir] ) {
+			if ( cur.nodeType === 1 && ++num === result ) {
+				break;
+			}
+		}
+
+		return cur;
+	},
+
+	sibling: function( n, elem ) {
+		var r = [];
+
+		for ( ; n; n = n.nextSibling ) {
+			if ( n.nodeType === 1 && n !== elem ) {
+				r.push( n );
+			}
+		}
+
+		return r;
+	}
+});