GDB/MI Varobj support for Ada

[Joel Brobecker]

Hello,

This patch series brings varobj support to Ada. Basically, the bulk
of the work is to make sure that the Ada objects get decoded properly.

The series also introduces a language-specific piece for type mutation.
It takes the easy road, one which I believe front-ends should be able
to understand without difficult, and might actually already work, if
they already supported floating varobjs.

This will also require a NEWS entry, which I will post as soon as
the patch is in.