Fix copy / move behaviour of Maps object.

Currently, moving or copying a Maps object leads to double free of MapInfo.

Even moving a Maps object  did not prevent this, as after a move
the object only has to be in an "unspecified but valid state", which can
be the original state for a vector of raw pointers (but not for a vector
of unique_ptrs).

Changing to unique_ptrs is the most failsafe way to make sure we never
accidentally destruct MapInfo.

Test: atest libuwindstack_test
      Failed LocalUnwinderTest#unwind_after_dlopen which also fails at master.

Change-Id: Id1c9739b334da5c1ba532fd55366e115940a66d3
diff --git a/debuggerd/libdebuggerd/tombstone.cpp b/debuggerd/libdebuggerd/tombstone.cpp
index 8798ad3..c08afda 100644
--- a/debuggerd/libdebuggerd/tombstone.cpp
+++ b/debuggerd/libdebuggerd/tombstone.cpp
@@ -316,7 +316,7 @@
   std::shared_ptr<unwindstack::Memory>& process_memory = unwinder->GetProcessMemory();
 
   std::string line;
-  for (unwindstack::MapInfo* map_info : *maps) {
+  for (auto const& map_info : *maps) {
     line = "    ";
     if (print_fault_address_marker) {
       if (addr < map_info->start) {