[Ada/DWARF] printing array of variant records

[Joel Brobecker]

Hello,

This patch series aims at enhancing GDB when printing arrays of
records whose contents and size is dynamic, in the case where
we're relying purely on standard DWARF info (no GNAT encodings).

The patch series has been tested on x86_64-linux using the FSF
testsuite, as well as a number of other platforms (Solaris, Windows,
crosses) using AdaCore's testsuite.

Most patches are small fixes and enhancements. Patch #2 (Add valaddr
support in dynamic property resolution) is interesting, thought,
as it is one answer to a question I asked at the very beginning
when we started reviewing patches introducing the concept of dynamic
type resolution: what if the data is not stored in inferior memory?
As it turns out, this patch series encounters one such case, because
we're dealing with data that is not necessarily byte-aligned. And
AdaCore also encountered another situation, with a function returning
a reference to a dynamic object, with that reference being returned
by register; hence no address either. Patch #2 enhances our framework
by using the contents-and-address idea.

If there are no objections, I'd like to commit the patch series
sometime early next week.

Thanks!