[Ada] Make the ATCB type info program-space-specific

[Ada] Make the ATCB type info program-space-specific

This module caches the type description of various elements of
the Ada Task Control Block (ATCB). This cache was implemented
as static globals, which is wrong in the case where we have
multiple inferiors. This change cleans things up a bit by moving
some of these static globals to a per-program-space area.

gdb/ChangeLog:

        * ada-tasks.c: #include "progspace.h" and "objfiles.h".
        (atcb_type, atcb_common_type, atcb_ll_type, atcb_call_type)
        (atcb_fieldno): Delete these static globals.
        (struct ada_tasks_pspace_data): New struct.
        (ada_tasks_pspace_data_handle): New static global.
        (get_ada_tasks_pspace_data): New function.
        (ada_tasks_invalidate_pspace_data): New function.
        (get_tcb_types_info, ptid_from_atcb_common, read_atcb)
        (read_known_tasks_list, ada_new_objfile_observer): Adjust.
        (_initialize_tasks): Create this module's per-progspace
        data handle.