Merge 1.5.4 changes back to master.

extensions/guacamole-auth-totp/pom.xml

@@ -162,12 +162,12 @@
         <dependency>
             <groupId>com.google.zxing</groupId>
             <artifactId>javase</artifactId>
-            <version>3.5.1</version>
+            <version>3.5.2</version>
         </dependency>
         <dependency>
             <groupId>com.google.zxing</groupId>
             <artifactId>core</artifactId>
-            <version>3.5.1</version>
+            <version>3.5.2</version>
         </dependency>
 
         <!-- Guacamole depends on an implementation of JAX-WS -->