[Dillo-dev] exit codes

I checked what bash sees when dillo returns -1 for bad cmdline argument, and $? shows 255. It seems that out of range values turn into 255. Not that anyone will ever care beyond zero vs nonzero, but I'd like to change it to something valid. I could change it to 1...or 2...or I could use the values from sysexits.h (i.e., borrow their values as opposed to including it, since it doesn't appear to be standard). Any opinions?