Allow directory bookmarks to be relative to Data_directory
see http://pulkomandy.tk/projects/GrafX2/ticket/45 Still to do : the "Set Rel" which is the difficult part :) Also it may be better to use Program_directory instead of Data_directory
I knew I forgot about something in my list of quirks!
Amiga platforms do not use ".." to denote the parent directory, they use "/". And they don't have anything to denote the current directory: instead absolute paths start with "volume_name:"
So, it may not be a good idea to rely on UNIX-style paths here.