* rcfile.c (parse_include): Abort on being unable to open an included rcfile.  Fixes
          Savannah bug 25490, nanorc: "include"ing a file which doesn't exist causes nano to segfault.



git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@4365 35c25a1d-7b9e-4130-9fde-d3aeb78583b8