tests: add fdatasync.test

* tests/fdatasync.c: New file.
* tests/fdatasync.test: New test.
* tests/.gitignore: Add fdatasync.
* tests/Makefile.am (check_PROGRAMS): Likewise.
(DECODER_TESTS): Add fdatasync.test.
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 4d18fe6..da97271 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -86,6 +86,7 @@
 	fchmod \
 	fcntl \
 	fcntl64 \
+	fdatasync \
 	file_handle \
 	filter-unavailable \
 	flock \
@@ -272,6 +273,7 @@
 	fchmod.test \
 	fcntl.test \
 	fcntl64.test \
+	fdatasync.test \
 	file_handle.test \
 	flock.test \
 	fstat.test \