For statements of just an unadorned VALUES clause, assign column names
as "columnN" for increasing whole numbers N.
In the command-line shell, defend against a NULL-pointer dereference in the
case where sqlite3_column_name() returns NULL (as might happen following an
OOM error).
For the Win32 VFS, defining winShmMutexHeld should be controlled by NDEBUG, not SQLITE_DEBUG.
Fix harmless compiler warning in LEMON.