This pointer is the first argument received by callbacks, and the
existing argument "data" is now automatically freed by WeeChat when the
object containing the callback is removed.
With this new pointer, the linked list of callbacks in scripts has been
removed. This will improve speed of scripts (using a lot of hooks),
reduce memory used by scripts and reduce time to unload scripts.
Following functions are affected in the C API:
* exec_on_files
* config_new
* config_new_section
* config_new_option
* hook_command
* hook_command_run
* hook_timer
* hook_fd
* hook_process
* hook_process_hashtable
* hook_connect
* hook_print
* hook_signal
* hook_hsignal
* hook_config
* hook_completion
* hook_modifier
* hook_info
* hook_info_hashtable
* hook_infolist
* hook_hdata
* hook_focus
* unhook_all_plugin
* buffer_new
* bar_item_new
* upgrade_new
* upgrade_read
New features:
- add optional hdata name for variables in hdata
- add plugin API functions: hdata_get_var_hdata
- use hashtable to store hdata (created by WeeChat and plugins)
- free hdata and infolists created by plugin on plugin unload
- free all hdata on exit
- add "free" option to command /debug hdata
- remove hdata for hooks