tests: check decoding and dumping of send and recv syscalls

* tests/unix-pair-send-recv.c: New file.
* tests/unix-pair-send-recv.expected: Likewise.
* tests/unix-pair-send-recv.test: New test.
* tests/.gitignore: Add unix-pair-send-recv.
* tests/Makefile.am (check_PROGRAMS): Likewise.
(DECODER_TESTS): Add unix-pair-send-recv.test.
(EXTRA_DIST): Add unix-pair-send-recv.expected.
diff --git a/tests/.gitignore b/tests/.gitignore
index 68d2f3b..c9e6219 100644
--- a/tests/.gitignore
+++ b/tests/.gitignore
@@ -282,6 +282,7 @@
 umovestr2
 umovestr3
 uname
+unix-pair-send-recv
 unix-pair-sendto-recvfrom
 unlink
 unlinkat