Version 2.9.0

Added

• Support for reading OPL files.
• For diff output OSM objects in buffers can be marked as only in one or the
  other file. The OPL and debug output formats support diff output based on
  this.
• Add documentation and range checks to Tile struct.
• More documentation.
• More examples and more extensive comments on examples.
• Support for a progress report in osmium::io::Reader() and a ProgressBar
  utility class to use it.
• New OSMObject::set_timestamp(const char*) function.

Changed

• Parse coordinates in scientific notations ourselves.
• Updated included protozero version to 1.4.2.
• Lots of one-argument constructors are now explicit.
• Timestamp parser now uses our own implementation instead of strptime.
  This is faster and independant of locale settings.
• More cases of invalid areas with duplicate segments are reported as
  errors.

Fixed

• Fixed a problem limiting cache file sizes on Windows to 32 bit.
• Fixed includes.
• Exception messages for invalid areas do not report "area contains no rings"
  any more, but "invalid area".