-Removed Cheat menu and replaced it with "Cheats..." menu item in the Options menu.
-Modified alert_message and confirm_message so they handle line wrap of the message internally, so now it's no longer necessary to insert newline chars into strings passed to alert_message and confirm_message.
-added list_find_node utility function to util.c.
-added utility functions to create/delete cheat structures for use by the gui.
stub: void lowercase(char string[]);
modified the screenshot function to use the roms header (without spaces, and converted to lowercase) name:
example: supermario64_001.png
-Added new tab to configuration dialog for user to create mappings.
-Minor fix: Reset configuration dialog to have first tab selected everytime it's shown.
