Fix a bug involving
frequent changes in and out of WAL mode and
VACUUM that could (in theory) cause database corruption.
Enhance the sqlite3_trace() mechanism so that nested SQL statements
such as might be generated by virtual tables are shown but are shown
in comments and without parameter expansion. This
greatly improves tracing output when using the FTS3/4 and/or RTREE
virtual tables.
Change the xFileControl() methods on all built-in VFSes to return
SQLITE_NOTFOUND instead of SQLITE_ERROR for an unrecognized
operation code.