Review clang analyzer warnings

We have a clang-analyzer build of WiredTiger running in Jenkins, but aren't actively tracking the reported failures. The job is:

http://build.wiredtiger.com:8080/job/wiredtiger-clang-analyzer/

Ideally we would:

• Review the currently reported warnings.
• Fix those that are real errors.
• Add a suppression catalog for the remaining warnings.
• Switch the Jenkins job so that it reports a failure when warnings are generated.