Limit allowed nesting layers in print_xxx;

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (1dd6f68) 99.70% compared to head (9620c41) 99.70%.

:exclamation: Current head 9620c41 differs from pull request most recent head 365fdc9. Consider uploading reports for the commit 365fdc9 to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #36 +/- ## ======================================= Coverage 99.70% 99.70% ======================================= Files 9 10 +1 Lines 668 689 +21 ======================================= + Hits 666 687 +21 Misses 2 2 ``` | [Impacted Files](https://app.codecov.io/gh/rnpgp/sexp/pull/36?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=rnpgp) | Coverage Δ | | |---|---|---| | [include/sexp/sexp.h](https://app.codecov.io/gh/rnpgp/sexp/pull/36?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=rnpgp#diff-aW5jbHVkZS9zZXhwL3NleHAuaA==) | `100.00% <100.00%> (ø)` | | | [src/sexp-depth-manager.cpp](https://app.codecov.io/gh/rnpgp/sexp/pull/36?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=rnpgp#diff-c3JjL3NleHAtZGVwdGgtbWFuYWdlci5jcHA=) | `100.00% <100.00%> (ø)` | | | [src/sexp-input.cpp](https://app.codecov.io/gh/rnpgp/sexp/pull/36?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=rnpgp#diff-c3JjL3NleHAtaW5wdXQuY3Bw) | `100.00% <100.00%> (ø)` | | | [src/sexp-object.cpp](https://app.codecov.io/gh/rnpgp/sexp/pull/36?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=rnpgp#diff-c3JjL3NleHAtb2JqZWN0LmNwcA==) | `98.55% <100.00%> (ø)` | | | [src/sexp-output.cpp](https://app.codecov.io/gh/rnpgp/sexp/pull/36?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=rnpgp#diff-c3JjL3NleHAtb3V0cHV0LmNwcA==) | `100.00% <100.00%> (ø)` | |

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