Change uses of Unchecked_Conversion (which is obsolete since Ada 95) to
Ada.Unchecked_Conversion to avoid warnings recently enabled in GNAT. Same
for Unchecked_Deallocation.
Previous patch only changed files used for production build; this patch
changes files used for debug builds (and also for gnatsocks, for
completeness).
no-precommit-check (to avoid complains about copyright headers)
Change-Id: I0a753b06a46ce56778b8de9c96607515bea7cf84