Modify the way some internal file-controls are invoked. In order to support multi-file transactions in the zipvfs extension.
Fix handling of errors returned by the SQLITE_FCNTL_OMIT_SYNCED file-control.
Merge changes from the trunk.
Use SQLITE_FCNTL_SYNC instead of SQLITE_FCNTL_SYNC_OMITTED. Add documentation in for FCNTL_SYNC and FCNTL_COMMIT_PHASETWO.
Fix harmless compiler warnings.
Have the crash-test infrastructure code in test6.c read and write the 512-byte block containing the pending-byte lock as normal. Earlier versions did not access this part of the file in order to avoid triggering an assert in os_unix.c. But the assert() has since been removed. And not reading/writing this part of the file causes problems for multiplexor tests.
Remove an unreachable conditional inserted by the previous check-in.
Fix a bug in the shell ".import" command:  Do not end the field
when an escaped double-quote occurs at the end of a CRNL line.
Merge in the latest trunk changes.
Add the SQLITE_FCNTL_SYNC and SQLITE_FCNTL_COMMIT_PHASETWO file-controls
and have the pager call them at appropriate times.  This is needed in order
to enable ZIPVFS to do multi-file atomic commits.