Add deferred_warnings parameter to read_addrmap_from_aranges

Add deferred_warnings parameter to read_addrmap_from_aranges

When DWARF reading is done in the background,
read_addrmap_from_aranges will be called from a worker thread.
Because warnings can't be emitted from these threads, this patch adds
a new deferred_warnings parameter to the function, letting the caller
control exactly how the warnings are emitted.