Non bit-packed packed arrays as variable-length fields

Non bit-packed packed arrays as variable-length fields

In the case of non bit-packed arrays, GNAT does not generate its
traditional XP encoding; it is not needed. However, it still generates
the so-called "implementation type" with a P suffix. This
implementation type shall be skipped when looking for other
descriptive types such as XA encodings for variable-length
fields.

Note also that there may be an intermediate typedef between the
implementation type and its XA description. It shall be skipped
as well.

gdb/ChangeLog:

        Jerome Guitton  <guitton@adacore.com>
	* ada-lang.c (find_parallel_type_by_descriptive_type):
	Go through typedefs during lookup.
	(to_fixed_array_type): Add support for non-bit packed arrays
	as variable-length fields.

gdb/testsuite/ChangeLog:

        * gdb.ada/byte_packed_arr: New testcase.