middle-end/97855 - avoid recursing into pp_printf

middle-end/97855 - avoid recursing into pp_printf

When diagnostic messages use pretty-printer formats like %D or %E
the pp_printf invocation can end up in tree pretty-printers which
then have to avoid using pp_printf themselves since this function
is not re-entrant.

The following removes all pp_printf uses from tree-pretty-print.c
fixing the observed malformed diagnostics.  It also poisons the
identifier so new uses are less likely to creep in.

2021-03-04  Richard Biener  <rguenther@suse.de>

	PR middle-end/97855
	* tree-pretty-print.c: Poison pp_printf.
	(dump_decl_name): Avoid use of pp_printf.
	(dump_block_node): Likewise.
	(dump_generic_node): Likewise.