[Ada] Full view of tagged type with ptype

[Ada] Full view of tagged type with ptype

When evaluating an expression, if it is of a tagged type, GDB reads
the tag in memory and deduces the full view. At parsing time, however,
this operation is done only in the case of OP_VAR_VALUE. ptype does
not go through a full evaluation of expressions so it may return some
odd results:

 (gdb) print c.menu_name
 $1 = 0x0
 (gdb) ptype $
 type = system.strings.string_access
 (gdb) ptype c.menu_name
 type = <void>

This change removes this peculiarity by extending the tag resolution
to UNOP_IND and STRUCTOP_STRUCT. As in the case of OP_VAR_VALUE, this
implies switching from EVAL_AVOID_SIDE_EFFECTS to EVAL_NORMAL when a
tagged type is dereferenced.

gdb/
	* ada-lang.c (ada_evaluate_subexp): Resolve tagged types to
	full view in the case of UNOP_IND and STRUCTOP_STRUCT.

gdb/testsuite/

	* gdb.ada/tagged_access: New testcase.