* ada-tasks.c: Rename build_task_list to ada_build_task_list, and

	* ada-tasks.c: Rename build_task_list to ada_build_task_list, and
	make it non-static.
	* ada-lang.h (task_control_block): declaration moved from ada-task.c
	to ada-lang.h; this is needed to be able to implement the kill command
	in multi-task mode.
	(task_ptid): Ditto.
	(task_entry): Ditto.
	(task_list): Ditto.
	(ada_build_task_list): Ditto.

	* ada-lang.c: Conditionalize routines and data structures related
	to breakpoints, exceptions, completion, and symbol caching on
	GNAT_GDB, since these are not yet used in the submitted public sources.
	(ada_main_name): Editorial: Move definition out of exception-related
	code.