Avoid overuse of name "buffer" in tree-pretty-print.c

Avoid overuse of name "buffer" in tree-pretty-print.c

gcc/ChangeLog:
	* tree-pretty-print.c (INDENT): Rename "buffer" to "pp".
	(NIY): Likewise.
	(buffer): Rename this variable to...
	(tree_pp): ...this.

	(do_niy): Rename param from "buffer" to "pp".
	(dump_decl_name): Likewise.
	(dump_function_name): Likewise.
	(dump_function_declaration): Likewise.
	(dump_array_domain): Likewise.
	(dump_omp_clause): Likewise.
	(dump_omp_clauses): Likewise.
	(dump_location): Likewise.
	(dump_block_node): Likewise.
	(dump_generic_node): Likewise.
	(print_declaration): Likewise.
	(print_struct_decl): Likewise.
	(print_call_name): Likewise.
	(pretty_print_string): Likewise.
	(newline_and_indent): Likewise.

	(print_generic_decl): Update for renaming of "buffer" to
	"tree_pp".
	(print_generic_stmt): Likewise.
	(print_generic_stmt_indented): Likewise.
	(print_generic_expr): Likewise.
	(maybe_init_pretty_print): Likewise.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@218405 138bc75d-0d04-0410-961f-82ee72b054a4