Remove usages of std::iterator in libunwindstack

std::iterator is deprecated in C++17, and it's presence in
libunwindstack is blocking upgrading libc++ in Chrome (since Chrome
builds with -Wdeprecated and -Werror).

Bug: chromium:1273285
Change-Id: I0e3ec4dcc109262b0ed95467d426441a6903e801
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/third_party/libunwindstack/+/3638767
Reviewed-by: Mike Wittman <wittman@chromium.org>
4 files changed