Update to ASM 6.0, which is necessary for Java 9.

Change-Id: I090e9a5b823618eff5e31ecb6e3ac67d89a8669c
diff --git a/maven/poms/gwt/pom-template.xml b/maven/poms/gwt/pom-template.xml
index 2ee0ca8..e0ba652 100644
--- a/maven/poms/gwt/pom-template.xml
+++ b/maven/poms/gwt/pom-template.xml
@@ -89,7 +89,7 @@
             <dependency>
                 <groupId>org.ow2.asm</groupId>
                 <artifactId>asm-parent</artifactId>
-                <version>5.0.3</version>
+                <version>6.0</version>
                 <type>pom</type>
                 <scope>import</scope>
             </dependency>