tests: extend test coverage of setuid32 syscall

* tests/setuid32.c: New file.
* tests/setuid32.test: New test.
* tests/.gitignore: Add setuid32.
* tests/Makefile.am (check_PROGRAMS): Likewise.
(DECODER_TESTS): Add setuid32.test.
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 854d182..592c2b7 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -194,6 +194,7 @@
 	set_ptracer_any \
 	sethostname \
 	setuid \
+	setuid32 \
 	shmxt \
 	sigaction \
 	sigaltstack \
@@ -402,6 +403,7 @@
 	sendfile64.test \
 	sethostname.test \
 	setuid.test \
+	setuid32.test \
 	shmxt.test \
 	sigaction.test \
 	sigaltstack.test \