Class file writing

Constant field initializers, annotations, and a bunch of constant pool
entry kinds are absent, we won't need them for a bit.

MOE_MIGRATED_REVID=133635333
diff --git a/pom.xml b/pom.xml
index c7596a8..e7edf35 100644
--- a/pom.xml
+++ b/pom.xml
@@ -37,6 +37,12 @@
       <scope>test</scope>
     </dependency>
     <dependency>
+      <groupId>org.ow2.asm</groupId>
+      <artifactId>asm-util</artifactId>
+      <version>5.0.3</version>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
       <groupId>com.google.errorprone</groupId>
       <artifactId>javac</artifactId>
       <version>1.9.0-dev-r2973-2</version>