PR jit/63854: Fix double-initialization within tree-pretty-print.c

PR jit/63854: Fix double-initialization within tree-pretty-print.c

gcc/ChangeLog:
	PR jit/63854
	* tree-pretty-print.c: Eliminate include of <new>.
	(buffer): Convert this variable from a pretty_printer to a
	pretty_printer *.
	(initialized): Eliminate this variable in favor of the NULL-ness
	of "buffer".
	(print_generic_decl): Update for "buffer" becoming a pointer.
	(print_generic_stmt): Likewise.
	(print_generic_stmt_indented): Likewise.
	(print_generic_expr): Likewise.
	(maybe_init_pretty_print): Likewise, allocating "buffer" on the
	heap and using its non-NULL-ness to ensure idempotency.

From-SVN: r218404