tests: check decoding of chown syscall

* tests/chown.c: New file.
* tests/chown.test: New test.
* tests/xchownx.c: New file.
* tests/.gitignore: Add chown.
* tests/Makefile.am (check_PROGRAMS): Likewise.
(DECODER_TESTS): Add chown.test.
(EXTRA_DIST): Add xchownx.c.
diff --git a/tests/.gitignore b/tests/.gitignore
index 6aae5de..ad27043 100644
--- a/tests/.gitignore
+++ b/tests/.gitignore
@@ -16,6 +16,7 @@
 bpf
 caps
 chmod
+chown
 chroot
 clock_nanosleep
 clock_xettime