
fl_file_chooser is a FLTK function which shows a file browser
window specifically intended for choosing a regular file.

fltk.fl_file_chooser(title,filename_filter,start_path,relative)

"relative" is a toggle. Non-zero means the filename returned will be a
path relative to your current location, and zero returns absolute path.

Using nil as start path will default to the previously chosen path,
or current directory if this is the first time the function is called

The filename filter is a string which filters the displayed files.
For example, "*.txt" would show only files ending with .txt and
"*.{gif,GIF,jpg,JPG,jpeg,JPEG,png,PNG,bmp,BMP,pict,PICT,p?m,P?M}"
would cover a number of image filenames.
