Add OrmException(Throwable) constructor variant

Some applications may find it useful for throwing checked
exceptions out of an OrmRunnable method.

Signed-off-by: Shawn O. Pearce <sop@google.com>
diff --git a/src/main/java/com/google/gwtorm/client/OrmException.java b/src/main/java/com/google/gwtorm/client/OrmException.java
index 72cb144..7a7fa5b 100644
--- a/src/main/java/com/google/gwtorm/client/OrmException.java
+++ b/src/main/java/com/google/gwtorm/client/OrmException.java
@@ -25,4 +25,8 @@
   public OrmException(final String message, final Throwable why) {
     super(message, why);
   }
+
+  public OrmException(final Throwable why) {
+    super(why);
+  }
 }