Standardize the error messages generated by constraint failures to a format
of "$TYPE constraint failed: $DETAIL".  This involves many changes to the
expected output of test cases.
Add tests for updates of without-rowid tables that use non-BINARY collation sequences for the primary key columns. And a minor bugfix to the same.
Updates to the backcompat.test test script so that it works with really old (3.6.*) versions.
Unless the destination table is completely empty, disable the xfer optimization for WITHOUT ROWID tables.
Remove an "explain" command from test script without_rowid1.test that was accidentally committed.
Fix a bug in secondary index initialization when the secondary index is
a superset of the PRIMARY KEY for a WITHOUT ROWID table.
Fix conflict handling for the case when the rowid uses REPLACE but other
unique constraints use FAIL or IGNORE.
Make sure the query planner knows that the PRIMARY KEY index of a
WITHOUT ROWID table is always a covering index.
Remove an unused variable.