bind,internal/importers: handle Java long constants correctly

Change-Id: Idff789038e7470ef5b12798273fc67165d57f4dc
Reviewed-on: https://go-review.googlesource.com/35293
Reviewed-by: David Crawshaw <crawshaw@golang.org>

bind/testdata/java.java.golden

@@ -11,6 +11,19 @@ public interface F extends R {
     
 }
 
+// Java class java.L is a proxy for talking to a Go program.
+//   gobind -lang=java java
+//
+// File is generated by gobind. Do not edit.
+package java;
+
+import go.Seq;
+
+public interface L extends R {
+    public String toString();
+    
+}
+
 // Java class java.O is a proxy for talking to a Go program.
 //   gobind -lang=java java
 //
@@ -83,6 +96,19 @@ public abstract class Java {
         
         public native String toString();
     }
+    private static final class proxyL implements Seq.Proxy, L {
+        private final Seq.Ref ref;
+        
+        @Override public final int incRefnum() {
+              int refnum = ref.refnum;
+              Seq.incGoRef(refnum);
+              return refnum;
+        }
+        
+        proxyL(Seq.Ref ref) { this.ref = ref; }
+        
+        public native String toString();
+    }
     private static final class proxyO implements Seq.Proxy, O {
         private final Seq.Ref ref;