Temporarily reduce method count limit for dexing.

Summary:
We have seen issues where Buck is not counting a reference to a
method when tracking how full a .jar is.  While debugging this
issue, this change temporarily reduces the limit so the resulting
.jar will have slightly fewer methods so dx can handle it.

src/com/facebook/buck/dalvik/DalvikAwareOutputStreamHelper.java

diff --git a/src/com/facebook/buck/dalvik/DalvikAwareOutputStreamHelper.java b/src/com/facebook/buck/dalvik/DalvikAwareOutputStreamHelper.java
index b732898..f560667 100644
--- a/src/com/facebook/buck/dalvik/DalvikAwareOutputStreamHelper.java
+++ b/src/com/facebook/buck/dalvik/DalvikAwareOutputStreamHelper.java
@@ -38,7 +38,8 @@
  */
 public class DalvikAwareOutputStreamHelper implements ZipOutputStreamHelper {
 
-  private static final int MAX_METHOD_REFERENCES = 64 * 1024;
+  // TODO-mmarucheck (#3178515): remove the '-2' when we understand the missing references.
+  private static final int MAX_METHOD_REFERENCES = 64 * 1024 - 2;
 
   private final ZipOutputStream outStream;
   private final Set<String> entryNames = Sets.newHashSet();