Refinements to generic popup and color picker

Refinements to generic popup and color picker

*) The text part of a checkbox can now be clicked to toggle the option.
*) Typing <Enter> in single-line text edits is ignored
*) Using a spin button now sets focus to the affected text edit, with
the insert position at the end.
*) Using the sample field or an RGB button sets focus to the
corresponding text edit, with the insert position at the end.
*) The adjust buttons now work in reverse, with a D button for "darker".
*) Editing a color field causes the sample field to update to the new
color when you type <Enter>.
*) The color pickers now define a default color, which can be instated
by clicking on the sample field.
*) Fix some 64-bit pointer warnings