Patch cord.h to remove CRAN warning

[paleolimbot]

Closes #223.

This warning is occurring because Abseil does C++ trickery to inline character data into its "cord" data structure. S2 uses the "strings" module from Abseil for its logging and its text format parsing/generation. We explicitly turn off logging and don't use S2's text format and thus the piece of code in question is never called.

This "fix" just comments out the line and throws an exception if for some unforseen reason that method actually actually does get called. In that case the error should propagate up to the top level catch provided by Rcpp.

The real fix is to update Abseil; however, updating Abseil means we can no longer support C++11 (we're using the last version of Abseil that does support C++11; subsequent versions require C++14). That would mean that s2 (and its reverse dependency sf) may have trouble building on Centos 7 (e.g., many compute clusters). Centos 7 isn't EOL until June 2024, so it may be worth considering making s2 an optional dependency of sf instead of a hard one (cc @edzer ). There is a workaround (use something called devtoolset 8 which allows using the Centos 8 toolchain to compile stuff for Centos 7).

[codecov-commenter]

Codecov Report

Merging #228 (6405c00) into main (ab29592) will not change coverage.
The diff coverage is n/a.

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  Coverage   94.02%   94.02%           
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  Lines        3517     3517           
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  Hits         3307     3307           
  Misses        210      210           

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[edzer]

LGTM!

I'd be also OK moving to requiring C++14; people on CentOS7 will always install from source so could relatively easy install an older version of s2; we just shouldn't pin sf on the latest s2 release. But for now this is a great fix!