Upgrade libosmium to v2.15.6

third_party/libosmium/test/include/test_crc.hpp

@@ -0,0 +1,18 @@
+#ifndef OSMIUM_TEST_CRC_HPP
+#define OSMIUM_TEST_CRC_HPP
+
+#ifdef OSMIUM_TEST_CRC_USE_BOOST
+
+/* Use the CRC32 implementation from boost. */
+#include <boost/crc.hpp>
+using crc_type = boost::crc_32_type;
+
+#else
+
+/* Use the CRC32 implementation from zlib. */
+#include <osmium/osm/crc_zlib.hpp>
+using crc_type = osmium::CRC_zlib;
+
+#endif
+
+#endif // OSMIUM_TEST_CRC_HPP

third_party/libosmium/test/include/utils.hpp

@@ -2,6 +2,30 @@
 #include <cstdlib>
 #include <string>
 
+#ifndef _WIN32
+# include <unistd.h>
+# include <fcntl.h>
+
+// This function counts the number of open file descriptors. It is used in
+// some tests to make sure that we are not leaking file descriptors.
+inline int count_fds() noexcept {
+    int count = 0;
+    for (int fd = 0; fd < 100; ++fd) {
+        if (fcntl(fd, F_GETFD) == 0) {
+            ++count;
+        }
+    }
+    return count;
+}
+
+#else
+// Dummy for Windows which doesn't have fcntl
+inline int count_fds() noexcept {
+    return 0;
+}
+#endif
+
+
 inline std::string with_data_dir(const char* filename) {
     const char* data_dir = getenv("OSMIUM_TEST_DATA_DIR");