Fix build with GCC 13 (#6632)

Building with GCC 13 failed because for example std::int32_t
was not found. Porting guide [1] suggested to add explicit includes
for <cstdint> if necessary, so did just that.

[1]: https://gcc.gnu.org/gcc-13/porting_to.html

include/util/coordinate.hpp

@@ -33,6 +33,7 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include <boost/numeric/conversion/cast.hpp>
 
 #include <cstddef>
+#include <cstdint>
 #include <iosfwd> //for std::ostream
 #include <sstream>
 #include <string>

include/util/opening_hours.hpp

@@ -3,6 +3,7 @@
 
 #include <boost/date_time/gregorian/gregorian.hpp>
 
+#include <cstdint>
 #include <string>
 #include <vector>
 

include/util/query_heap.hpp

@@ -6,6 +6,7 @@
 #include <boost/optional.hpp>
 
 #include <algorithm>
+#include <cstdint>
 #include <limits>
 #include <map>
 #include <unordered_map>