Fix fortran build error on AIX.

	gcc/fortran/
	* parse.c (unexpected_eof): Call gcc_unreachable before return.

From-SVN: r254270

gcc/fortran/ChangeLog

+2017-10-31  Jim Wilson  <wilson@tuliptree.org>
+
+	* parse.c (unexpected_eof): Call gcc_unreachable before return.
+
 2017-10-30  Paul Thomas  <pault@gcc.gnu.org>
 
 	PR fortran/80850

gcc/fortran/parse.c

@@ -2737,6 +2737,9 @@ unexpected_eof (void)
   gfc_done_2 ();
 
   longjmp (eof_buf, 1);
+
+  /* Avoids build error on systems where longjmp is not declared noreturn.  */
+  gcc_unreachable ();
 }