Combo box with checked drop-down list

The CBCGPCheckComboBox class extends the functionality of CBCGPComboBox by supporting item check boxes.

Sample code:

CBCGPCheckComboBox m_wndComboBox;
...
// Check 1-st and 3-td items:
m_wndComboBox.SetCheck(0);
m_wndComboBox.SetCheck(2);

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