Namespace generated class names

Right now the bytecode module generates classnames that look like
com_facebook_presto_$gen_PageProcessor_28 with no package name. It's
annoying when you're trying to profile the code with VisualVM or the
like and you want to filter on package name.

presto-bytecode/src/main/java/com/facebook/presto/bytecode/CompilerUtils.java

@@ -55,9 +55,9 @@ private CompilerUtils()
 
     public static ParameterizedType makeClassName(String baseName)
     {
-        String className = "com.facebook.presto.$gen." + baseName + "_" + CLASS_ID.incrementAndGet();
+        String className = baseName + "_" + CLASS_ID.incrementAndGet();
         String javaClassName = toJavaIdentifierString(className);
-        return ParameterizedType.typeFromJavaClassName(javaClassName);
+        return ParameterizedType.typeFromJavaClassName("com.facebook.presto.$gen." + javaClassName);
     }
 
     public static String toJavaIdentifierString(String className)