backport: libiberty.h (xexit): Change decl to use modern GCC attribute to indicate exit does not return.

      * Merge devo and egcs include directories.
1998-08-03  Jason Molenda  (jsm@bugshack.cygnus.com)
      * libiberty.h (xexit): Change decl to use modern GCC attribute
      to indicate exit does not return.

From-SVN: r22942