unify PHPUnit config files

* add XML namespace attributes
* remove attributes using default values
* remove unknown `syntaxCheck` option

Author: xabbuh

phpunit.xml.dist

@@ -1,14 +1,9 @@
 <?xml version="1.0" encoding="UTF-8"?>
 
-<phpunit backupGlobals="false"
-         backupStaticAttributes="false"
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="http://schema.phpunit.de/4.1/phpunit.xsd"
+         backupGlobals="false"
          colors="true"
-         convertErrorsToExceptions="true"
-         convertNoticesToExceptions="true"
-         convertWarningsToExceptions="true"
-         processIsolation="false"
-         stopOnFailure="false"
-         syntaxCheck="false"
          bootstrap="vendor/autoload.php"
          failOnRisky="true"
          failOnWarning="true"