PR3672 cont'd: Change pretty-print "depth" to mean substructures
We don't follow pointers anymore within a structure. Now a single '$'
suffix means we print a shallow view of the structure, with {...} and
[...] in place of nested arrays/structs. A double suffix '$$' means we
print everything contained in the struct. Longer suffixes no longer
have meaning, and for now act the same as '$$'.
* tapsets.cxx (dwarf_pretty_print): Lose the "print_depth" field, and
instead just check if this is a "full" print job. Pass a bool
indicating whether we're currently traversing the top-level, so we
know which structs to expand. Also wrap it all in try/catch so bad
pointers don't kill us.