Summary:
As the C++ part exposes now SequenceNumber retrieval
for Snapshots we want this obviously also in the Java API.
Test Plan:
make rocksdbjava
make jtest
mvn -f rocksjni.pom test
Reviewers: yhchiang, adamretter, ankgup87
Subscribers: dhruba
Differential Revision: https://reviews.facebook.net/D32571
