Add scrollable cursor support to StatementOptions

[fdcastel]

Add scrollable cursor support to StatementOptions

Fixes asfernandes#25

Summary

Statement now supports opening scrollable cursors via a new CursorType option in StatementOptions. Previously, cursors were always opened with flag 0 (forward-only), which meant the scrollable fetch methods (fetchPrior, fetchFirst, fetchLast, fetchAbsolute, fetchRelative) would silently fail even though they were already exposed in the API.

Changes

Statement.h

• New CursorType enum with FORWARD_ONLY (default) and SCROLLABLE values.
• StatementOptions gains getCursorType() / setCursorType() with fluent API.
• Statement stores a cursorFlags member, initialized from StatementOptions in the constructor. The move constructor transfers it.

Statement.cpp

• Constructor: when CursorType::SCROLLABLE is set, stores IStatement::CURSOR_TYPE_SCROLLABLE in cursorFlags.
• execute(): passes cursorFlags (instead of hard-coded 0) to openCursor().

src/test/ScrollableCursor.cpp (new)

Seven test cases:

• Default cursor type is FORWARD_ONLY
• Scrollable cursor supports fetchFirst
• Scrollable cursor supports fetchLast
• Scrollable cursor supports fetchPrior
• Scrollable cursor supports fetchAbsolute
• Scrollable cursor supports fetchRelative
• Forward-only cursor works correctly with default options

Usage

// Scrollable cursor
Statement select{attachment, transaction, "select col from t order by col",
    StatementOptions().setCursorType(CursorType::SCROLLABLE)};
select.execute(transaction);
select.fetchLast();     // jump to last row
select.fetchFirst();    // jump back to first row
select.fetchAbsolute(3); // jump to row 3
select.fetchRelative(-1); // move back one row

// Forward-only cursor (default — unchanged behavior)
Statement select{attachment, transaction, "select col from t"};
select.execute(transaction);
while (select.fetchNext()) { /* ... */ }

Backward Compatibility

This is a non-breaking, additive change. The default cursor type is FORWARD_ONLY, preserving existing behavior. No existing API signatures are modified.