SOLR-5765: Update to SLF4J 1.7.6.
SOLR-5765: Update to SLF4J 1.7.6.

git-svn-id: 308d55f399f3bd9aa0560a10e81a003040006c48@1570951 13f79535-47bb-0310-9956-ffa450edef68

cscorley/solr-only-mirror,cscorley/solr-only-mirror,cscorley/solr-only-mirror