- Update to 2.18.0
* Use `system_error` instead of `runtime_error` where it fits better.
* Remove `OSMIUM_NORETURN` macro. This hasn't been used in a while.

### Removed deprecated parts of the code

Several parts of libosmium have been marked deprecated, many of them for a very
long time. These are now removed:

* Sparsehash index class `osmium::index::map::SparseMemTable` as well as the
complete file `osmium/index/map/sparse_mem_table.hpp`.
* Callback functionality of the `osmium::memory::Buffer` class. The
`set_full_callback()` will not be available any more. See the source
for replacement options.
* Various `osmium::builder::build_*` functions in
`osmium/builder/builder_helper.hpp`. Use `osmium::builder::add_*`
functions instead. Removes `builder_helper.hpp`.
* `osmium::builder::Builder::add_item(const osmium::memory::Item* item)`.
Use the function of the same name taking a reference instead.
* `osmium::builder::OSMObject/ChangesetBuilder::add_user()`. Use
`set_user()` instead.
* `osmium::builder::ChangesetBuilder::bounds()` returning a modifiable
reference. Use `set_bounds()` instead.
* Several functions around `osmium::io::OutputIterator`.
* `osmium::Area::inner_ring_cbegin/cend()`, use `inner_rings()` instead.
* `osmium::RelationMember::ref()`, use `set_ref()` instead.
* Implicit conversion from `osmium::Timestamp` to `std::time_t`. Use
`seconds_since_epoch()` instead.
* `osmium::string_to_user_id()`, use `string_to_uid` instead.
* `osmium::static_cast_with_assert()` helper functions as well as the
complete include file `osmium/util/cast.hpp`.
* Some constructors of `osmium::util::MemoryMapping` and
`osmium::util::TypedMemoryMapping`. Use other constructor instead.
- Update to 2.17.3
* Removed possible deadlock when shutting down active Reader.
- Update to 2.17.2
* Libosmium now supports being compiled in C++17 and C++20 mode. The minimum
version required is still C++11, but if you use libosmium in an C++17 or
C++20 application this should work properly.
* Switch from catch version 1 to catch2 as test framework.
* When `std::variant` is available (C++17 and above), libosmium will use that
instead of `boost::variant` reducing the dependencies a little bit.
* Remove use of `boost::filter_iterator` and `boost::indirect_iterator`. The
removes the dependency on Boost Iterator.
* When ordering OSM objects (mostly use in the `CheckOrder` handler), the
smallest id possible (`INTMIN`) wasn't sorted correctly.
* Threading problem when reading files.
* Possible dereference of invalid iterator in legacy area assembler. This
only affects the legacy area assembler that takes old-style multipolygons
into account, so modern code that is not working with history data is not
affected.
* Fixed read from an empty queue when reading a file which could block
libosmium forever when an error was encountered while reading a file.
* As always: Various small code cleanups.
- Packaging:
* Drop signal.diff patch, no longer required.
* Add liblz4 to BuildRequires