Added pragma support for controlling proxy file locking
Added file control access to last errno and proxy locking
Added support for TMPDIR environment variable
Extended unit tests to cover new proxy locking pragmas and file control features (CVS 5934)
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of the sqlite3_file_control() interface, and in particular make sure
the interface works on :memory: databases. (CVS 4738)
FossilOrigin-Name: 83ca4fc7dc18d6deca58fe4181905eb9754e03da