update to 3.6.21
changes:
-SQL output resulting from sqlite3_trace() is now modified to include
the values of bound parameters
-Performance optimizations targetting a specific use case from a single
high-profile user
-FTS3 extension has undergone a major rework and cleanup
-fixed the SQLITE_SECURE_DELETE compile-time option
-Improvements to "dot-command" handling in the Command Line Interface
-Other minor bug fixes and documentation enhancements

(drochner)