Remove array typedef assumption for Ada

Currently the Ada code assumes that it can distinguish between a
multi-dimensional array and an array of arrays by looking for an
intervening typedef -- that is, for an array of arrays, there will be
a typedef wrapping the innermost array type.

A recent compiler change removes this typedef, which causes a gdb
failure in the internal AdaCore test suite.

This patch handles this case by checking whether the array type in
question has a name.