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.

tests/data_files/dir-maxpath/c01.pem

@@ -0,0 +1,24 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----