Enable posix_fadvise usage on FreeBSD

Author: AMDmi3

include/osmium/io/detail/read_write.hpp

@@ -253,7 +253,7 @@ namespace osmium {
              * needed again soon. Keeps the buffer cache clear for other
              * things.
              */
-#ifdef __linux__
+#if defined(__linux__) || defined(__FreeBSD__)
             inline void remove_buffered_pages(int fd) noexcept {
                 if (fd > 0) {
                     ::posix_fadvise(fd, 0, 0, POSIX_FADV_DONTNEED);
@@ -269,7 +269,7 @@ namespace osmium {
              * file that will not be needed again soon. Keeps the buffer cache
              * clear for other things.
              */
-#ifdef __linux__
+#if defined(__linux__) || defined(__FreeBSD__)
             inline void remove_buffered_pages(int fd, std::size_t size) noexcept {
                 constexpr const std::size_t block_size = 4096;
                 // Make sure to keep the last 10 blocks around, so were are

include/osmium/io/reader.hpp

@@ -248,7 +248,7 @@ namespace osmium {
 #endif
                 }
                 const int fd = osmium::io::detail::open_for_reading(filename);
-#if __linux__
+#if defined(__linux__) || defined(__FreeBSD__)
                 if (fd >= 0) {
                     // Tell the kernel we are going to read this file sequentially
                     ::posix_fadvise(fd, 0, 0, POSIX_FADV_SEQUENTIAL);