analyzer: workaround for nested pp_printf

analyzer: workaround for nested pp_printf

The dumps from the analyzer sometimes contain garbled output.

The root cause is due to nesting of calls to pp_printf: I'm using
pp_printf with %qT to print types with a PP using default_tree_printer.

default_tree_printer handles 'T' (and various other codes) via
  dump_generic_node (pp, t, 0, TDF_SLIM, 0);
and dump_generic_node can call pp_printf in various ways, leading
to a pp_printf within a pp_printf, and garbled output.

I don't think it's feasible to fix pp_printf to be reentrant, in
stage 4, at least, so for the moment this patch works around it
in the analyzer.

gcc/analyzer/ChangeLog:
	* region-model.cc (print_quoted_type): New function.
	(svalue::print): Use it to replace %qT.
	(region::dump_to_pp): Likewise.
	(region::dump_child_label): Likewise.
	(region::print_fields): Likewise.