SQLite supports three mode of thread safety, as describe in "SQLite And Multiple Threads" :
see http://www.sqlite.org/threadsafe.html
This SQLiteC++ wrapper does not add any lock (no mutexes) nor any other thread-safety mecanism
above the SQLite library itself, by design, for lightness and speed.
Thus, SQLiteC++ naturally supports the "Multi Thread" mode of SQLite ;
"In this mode, SQLite can be safely used by multiple threads
provided that no single database connection is used simultaneously in two or more threads."
But SQLiteC++ does not support the fully thread-safe "Serialized" mode of SQLite,
because of the way it shares the underling SQLite precompiled statement
in a custom shared pointer (See the inner class "Statement::Ptr").