tests: check decoding of sockaddr structures

* tests/net-sockaddr.c: New file.
* tests/net-sockaddr.test: New test.
* tests/.gitignore: Add net-sockaddr.
* tests/Makefile.am (check_PROGRAMS): Likewise.
(DECODER_TESTS): Add net-sockaddr.test.
diff --git a/tests/.gitignore b/tests/.gitignore
index 72e93d8..1771902 100644
--- a/tests/.gitignore
+++ b/tests/.gitignore
@@ -141,6 +141,7 @@
 nanosleep
 net-accept-connect
 net-icmp_filter
+net-sockaddr
 net-y-unix
 net-yy-inet
 net-yy-netlink