Update a couple of test cases to account for the fact that ROLLBACK does not always abort all running SELECT statements.
Fix a bug in the sqlite3TripAllCursors() routine that prevents it from
reporting errors.  It is unknown at this time whether or not this omission can
result in any incorrect result in an actual query.
When a SELECT statement is terminated by a ROLLBACK TO operation, make the
error message be "abort due to ROLLBACK" rather than 
"callback requested query abort".
Improved comments on the BtCursor.skipNext field.  No changes to code.
Avoid calling sqlite3BtreeKeysize() on a b-tree cursor in SKIPNEXT or SKIPPREV state.
Remove code from sqlite3BtreeKeySize() made unreachable by the previous
check-in.
Add an ALWAYS() to an always-true conditional in the WAL rollback logic.