tests: use errno2name()

Automatically change tests/*.c files using the following sed regexp:
sed -i 's/errno == E[[:alnum:]]\+ ? "E[[:alnum:]]\+" : "E[[:alnum:]]\+"/errno2name()/g'
diff --git a/tests/fchdir.c b/tests/fchdir.c
index c9153a2..4051117 100644
--- a/tests/fchdir.c
+++ b/tests/fchdir.c
@@ -14,7 +14,7 @@
 
 	long rc = syscall(__NR_fchdir, fd);
 	printf("fchdir(%d) = %ld %s (%m)\n",
-	       (int) fd, rc, errno == ENOSYS ? "ENOSYS" : "EBADF");
+	       (int) fd, rc, errno2name());
 
 	puts("+++ exited with 0 +++");
 	return 0;