[Ada/tasks] Optimize ATCB lookups

[Ada/tasks] Optimize ATCB lookups

Type symbols that are used to decode the Ada task control block may be
duplicated in any unit that uses a tasking feature; an Ada lookup of
these symbols would collect all the duplicated instances and could
provoke the load of a huge amount of debug symbols in the process.

However, when decoding the task information, we are only interested in
one instance; and we have the full name of the symbol anyway. So use
a C lookup instead of an Ada lookup.

2010-11-05  Jerome Guitton  <guitton@adacore.com>

	* ada-tasks.c (get_tcb_types_info): Use C lookups to get
	ATCB symbols.