Support liburing without io_uring_free_probe()

See liburing commit 834496358870cb272f98cf22b3fe0307c83a526d

configure.ac

@@ -85,6 +85,10 @@ AM_CONDITIONAL(HAVE_URING,[test "x$ac_cv_header_liburing_h" != "xno"])
 AM_CONDITIONAL(HAVE_ASYNCH,[test "x$ac_cv_header_sys_asynch_h" != "xno"])
 
 AC_CHECK_FUNCS([fallocate])
+save_LIBS="${LIBS}"
+LIBS="${LIBS} -luring"
+AC_CHECK_FUNCS([io_uring_free_probe])
+LIBS="${save_LIBS}"
 
 PKG_CHECK_MODULES([XXHASH], [libxxhash], [], [true])
 # avoiding the fruitless RPATH debate for now

src/fellow_io_uring.c

@@ -35,6 +35,10 @@
 #include "vdef.h"
 #include "vas.h"
 
+#ifndef HAVE_IO_URING_FREE_PROBE
+#define io_uring_free_probe(x) free(x)
+#endif
+
 #include "fellow_io_backend.h"
 #include "fellow_io_ioctl.h"