(walk_tree_symbol): Use evallen and evalue instead of
vallen & value because of corresponding changes in
sysroff.info.
* sysdump.c (sysroff_swap_tr_in, sysroff_print_tr_out): New
functions.
* sysroff.info (tr): the tr block is a special case --- a block
without contents --- which can't be handled by generated code.
(den, dpp): only first byte is present for DENend, DPPend.
(dsy): describe a conditional portion of block, rename some fields.
(dps): describe a conditional portion of block.
(dfl): removed.
* sysinfo.y (yyerror): write error message to standard error.
