Db2 for IBM i 1.9.4

What's Changed

• Cleanup API changes and fix ASP info by @worksofliam in #344
• Add check for Merge statement by @worksofliam in #349
• Add simple try catch to updatable check by @worksofliam in #350
• Support for null in small columns by @worksofliam in #351

Full Changelog: 1.9.3...1.9.4