Reverted recent changes to make LLVS deployable on older OSes again.

Removed redundant @available and fixed minor compile issues on latest…

… Swift.

Added SQLitePerformanceTests.

Finished rewrite of README file, with new Quick Start.

Dropped back to requiring swift 5.0.

Dropped back to requiring swift 5.0.

Fixed a number of issues with public database CloudKit.

Fixed a number of issues with public database CloudKit.

Changed build platform to iphoneos for Cocoapods.

Changed build platform to iphoneos for Cocoapods.