tests: add munlockall.test

* tests/munlockall.c: New file.
* tests/munlockall.test: New test.
* tests/.gitignore: Add munlockall.
* tests/Makefile.am (check_PROGRAMS): Likewise.
(DECODER_TESTS): Add munlockall.test.
diff --git a/tests/.gitignore b/tests/.gitignore
index acf92c8..0eae082 100644
--- a/tests/.gitignore
+++ b/tests/.gitignore
@@ -126,6 +126,7 @@
 mmsg
 move_pages
 mq
+munlockall
 nanosleep
 net-accept-connect
 net-icmp_filter