Improved StAX<->SAX bridge

Improved the SAX to StAX (and vice-versa) bridge exposed via StaxUtils.
The old integration had some issues with namespace declaration
attributes, brought to light in a XMLUnit upgrade.

Issue: SPR-11549

Author: Arjen Poutsma

build.gradle

@@ -242,7 +242,7 @@ project("spring-core") {
 		optional("org.aspectj:aspectjweaver:${aspectjVersion}")
 		optional("net.sf.jopt-simple:jopt-simple:4.6")
 		optional("log4j:log4j:1.2.17")
-		testCompile("xmlunit:xmlunit:1.3")
+		testCompile("xmlunit:xmlunit:1.5")
 		testCompile("org.codehaus.woodstox:wstx-asl:3.2.7") {
 			exclude group: "stax", module: "stax-api"
 		}
@@ -460,7 +460,7 @@ project("spring-oxm") {
 		optional("org.codehaus.castor:castor-xml:1.3.2")
 		testCompile(project(":spring-context"))
 		testCompile("org.codehaus.jettison:jettison:1.0.1")
-		testCompile("xmlunit:xmlunit:1.3")
+		testCompile("xmlunit:xmlunit:1.5")
 		testCompile("xmlpull:xmlpull:1.1.3.4a")
 		testCompile(files(genCastor.classesDir).builtBy(genCastor))
 		testCompile(files(genJaxb.classesDir).builtBy(genJaxb))
@@ -567,7 +567,7 @@ project("spring-web") {
 		}
 		optional("log4j:log4j:1.2.17")
 		testCompile(project(":spring-context-support"))  // for JafMediaTypeFactory
-		testCompile("xmlunit:xmlunit:1.3")
+		testCompile("xmlunit:xmlunit:1.5")
 		testCompile("org.slf4j:slf4j-jcl:${slf4jVersion}")
 	}
 
@@ -703,7 +703,7 @@ project("spring-webmvc") {
 		}
 		testCompile(project(":spring-aop"))
 		testCompile("rhino:js:1.7R1")
-		testCompile("xmlunit:xmlunit:1.3")
+		testCompile("xmlunit:xmlunit:1.5")
 		testCompile("dom4j:dom4j:1.6.1") {
 			exclude group: "xml-apis", module: "xml-apis"
 		}
@@ -806,7 +806,7 @@ project("spring-test") {
 		optional("org.aspectj:aspectjweaver:${aspectjVersion}")
 		optional("org.hamcrest:hamcrest-core:1.3")
 		optional("com.jayway.jsonpath:json-path:0.9.0")
-		optional("xmlunit:xmlunit:1.3")
+		optional("xmlunit:xmlunit:1.5")
 		testCompile(project(":spring-context-support"))
 		testCompile(project(":spring-oxm"))
 		testCompile(project(":spring-webmvc-tiles3"))