C++ify osdata

C++ify osdata

This patch c++ifies the osdata structure: osdata_column, osdata_item and
osdata.  char* are replaced with std::string and VEC are replaced with
std::vector.  This allows to get rid of a great deal of cleanup and
free'ing code.

I replaced the splay tree in list_available_thread_groups with an
std::map.  Unless there's a good advantage to keep using a splay tree,
I think using the standard type should make things simpler to
understand.

gdb/ChangeLog:

	* osdata.h: Include vector isntead of vec.h.
	(osdata_column_s): Remove typedef.
	(struct osdata_column): Add constructor.
	<name, value>: Change type to std::string.
	(DEF_VEC_O (osdata_column_s)): Remove.
	(osdata_item_s): Remove typedef.
	(struct osdata_item) <columns>: Change type to std::vector.
	(DEF_VEC_O (osdata_item_s)): Remove.
	(struct osdata): Add constructor.
	<type>: Change type to std::string.
	<items>: Change type to std::vector.
	(osdata_p): Remove typedef.
	(DEF_VEC_P (osdata_p)): Remove.
	(osdata_parse): Return a unique_ptr.
	(osdata_free): Remove.
	(make_cleanup_osdata_free): Remove.
	(get_osdata): Return a unique_ptr.
	(get_osdata_column): Return pointer to std::string, take a
	reference to osdata_item as parameter.
	* osdata.c (struct osdata_parsing_data) <osdata>: Change type to
	unique_ptr.
	<property_name>: Change type to std::string.
	(osdata_start_osdata): Allocate osdata with new and adjust.
	(osdata_start_item): Adjust.
	(osdata_start_column): Adjust.
	(osdata_end_column): Adjust.
	(clear_parsing_data): Remove.
	(osdata_parse): Return a unique_ptr and adjust, remove cleanup.
	(osdata_item_clear): Remove.
	(get_osdata): return a unique_ptr and adjust.
	(get_osdata_column): Return a pointer to std::string and adjust.
	(info_osdata): Adjust.
	* mi/mi-main.c: Include <map>.
	(free_vector_of_osdata_items): Remove.
	(list_available_thread_groups): Adjust, use std::map instead of
	splay tree.