Added Mac OS X Checkboxes.
Added the alternate value as a parameter to Mac OS X sysData.make() in preparation for Comboboxes and Listboxes.
Added an alternate textsel for Mac OS X Comboboxes.
Added the beginning of the Mac OS X implementation of Combobox; also added a file to plan out how lists will be implemented/are being implemented.
Added the other Combobox modification functions to the Mac OS X backend. Before continuing, I'll get messageboxes working...
Added the Mac OS X implementation of messageboxes.
Finished the implementation of Combobox on Mac OS X.