Add test for limit on intermediate certificates

Inspired by test code provided by Nicholas Wilson in PR #351.

The test will fail if someone sets MAX_INTERMEDIATE_CA to a value larger than
18 (default is 8), which is hopefully unlikely and can easily be fixed by
running long.sh again with a larger value if it ever happens.

Current behaviour is suboptimal as flags are not set, but currently the goal
is only to document/test existing behaviour.
diff --git a/tests/data_files/dir-maxpath/18.crt b/tests/data_files/dir-maxpath/18.crt
new file mode 100644
index 0000000..afd682e
--- /dev/null
+++ b/tests/data_files/dir-maxpath/18.crt
@@ -0,0 +1,12 @@
+-----BEGIN CERTIFICATE-----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=
+-----END CERTIFICATE-----