Updated Xalan and XercesImpl dependencies.

Updated some JAXB-related dependencies to newer versions.
These upgrades are required to make the cobertura-maven-plugin work with JDK 7.

The project does still not build properly on Windows - which seems to be caused by Groovy's handling of the Ant Path class (more specifically: not translating \'s to \\'s). This implies a load of exceptions on the form:

```
simpleThreadTestWithIfStatement(net.sourceforge.cobertura.thread.test.ThreadedFunctionalTest)  Time elapsed: 41 sec  <<< ERROR!
Compilation Failed
        at org.codehaus.groovy.ant.Groovyc.compile(Groovyc.java:807)
        at org.codehaus.groovy.ant.Groovyc.execute(Groovyc.java:540)
        at net.sourceforge.cobertura.thread.test.ThreadedFunctionalTest.compileSource(ThreadedFunctionalTest.java:340)
        at net.sourceforge.cobertura.thread.test.ThreadedFunctionalTest.runTest(ThreadedFunctionalTest.java:274)
        at net.sourceforge.cobertura.thread.test.ThreadedFunctionalTest.simpleThreadTestWithIfStatement(ThreadedFunctionalTest.java:237
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:606)
        at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
        at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
        at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
        at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
        at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
        at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
        at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
        at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
        at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
        at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
        at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
        at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
        at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
        at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
        at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
        at org.apache.maven.surefire.junit4.JUnit4Provider.execute(JUnit4Provider.java:252)
        at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:141)
        at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:112)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:606)
        at org.apache.maven.surefire.util.ReflectionUtils.invokeMethodWithArray(ReflectionUtils.java:189)
        at org.apache.maven.surefire.booter.ProviderFactory$ProviderProxy.invoke(ProviderFactory.java:165)
        at org.apache.maven.surefire.booter.ProviderFactory.invokeProvider(ProviderFactory.java:85)
        at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:115)
        at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:75)
Caused by: org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed, Compile error during compilation with javac.
C:\Development\codehaus\cobertura\cobertura\target\tmp\cobertura\src\mypackage\Main.java:22: error: illegal escape character
                File instrumentDir = new File("C:\Development\codehaus\cobertura\cobertura\target\tmp\cobertura\instrument");
                                                  ^
C:\Development\codehaus\cobertura\cobertura\target\tmp\cobertura\src\mypackage\Main.java:22: error: illegal escape character
                File instrumentDir = new File("C:\Development\codehaus\cobertura\cobertura\target\tmp\cobertura\instrument");
                                                              ^
C:\Development\codehaus\cobertura\cobertura\target\tmp\cobertura\src\mypackage\Main.java:22: error: illegal escape character
                File instrumentDir = new File("C:\Development\codehaus\cobertura\cobertura\target\tmp\cobertura\instrument");
                                                                       ^
C:\Development\codehaus\cobertura\cobertura\target\tmp\cobertura\src\mypackage\Main.java:22: error: illegal escape character
                File instrumentDir = new File("C:\Development\codehaus\cobertura\cobertura\target\tmp\cobertura\instrument");
                                                                                 ^
C:\Development\codehaus\cobertura\cobertura\target\tmp\cobertura\src\mypackage\Main.java:22: error: illegal escape character
                File instrumentDir = new File("C:\Development\codehaus\cobertura\cobertura\target\tmp\cobertura\instrument");
                                                                                                      ^
C:\Development\codehaus\cobertura\cobertura\target\tmp\cobertura\src\mypackage\Main.java:22: error: illegal escape character
                File instrumentDir = new File("C:\Development\codehaus\cobertura\cobertura\target\tmp\cobertura\instrument");
                                                                                                                ^
C:\Development\codehaus\cobertura\cobertura\target\tmp\cobertura\src\mypackage\Main.java:23: error: illegal escape character
                File coberturaClassDir = new File("C:\Development\codehaus\cobertura\cobertura\target\test\cobertura_classes");
                                                      ^
C:\Development\codehaus\cobertura\cobertura\target\tmp\cobertura\src\mypackage\Main.java:23: error: illegal escape character
                File coberturaClassDir = new File("C:\Development\codehaus\cobertura\cobertura\target\test\cobertura_classes");
```