objcopy write_debugging_info memory leaks

The old stabs code didn't bother too much about freeing memory.
This patch corrects that and avoids some dubious copying of strings.

	* objcopy.c (write_debugging_info): Free both strings and
	syms on failure to create sections.
	* wrstabs.c: Delete unnecessary forward declarations and casts
	throughout file.
	(stab_write_symbol_and_free): New function.  Use it
	throughout, simplifying return paths.
	(stab_push_string): Don't strdup string.  Use it thoughout
	for malloced strings.
	(stab_push_string_dup): New function.  Use it throughout for
	strings in auto buffers.
	(write_stabs_in_sections_debugging_info): Free malloced memory.
	(stab_enum_type): Increase buffer sizing for worst case.
	(stab_range_type, stab_array_type): Reduce buffer size.
	(stab_set_type): Likewise.
	(stab_method_type): Free args on error return.  Correct
	buffer size.
	(stab_struct_field): Fix memory leaks.
	(stab_class_static_member, stab_class_baseclass): Likewise.
	(stab_start_class_type): Likewise.  Correct buffer size.
	(stab_class_start_method): Correct buffer size.
	(stab_class_method_var): Free memory on error return.
	(stab_start_function): Fix "rettype" memory leak.