PR summary

This PR removes curve_distance_epsilon from "src_agg_curves.cpp". As far as I can tell, this was present in the original agg 2.4 source but was never used.

It has generated a warning for at least the last decade, if not longer:

[7/33] Compiling C++ object extern/agg24-svn/libagg.a.p/src_agg_curves.cpp.o
../../extern/agg24-svn/src/agg_curves.cpp:24:18:
warning: unused variable 'curve_distance_epsilon' [-Wunused-const-variable]
    const double curve_distance_epsilon                  = 1e-30;

AI Disclosure

No AI used.

PR quality check

• Use an expressive title, e.g. "Fix title font property precedence"
• New and changed code is tested
• [N/A] Plotting related features are demonstrated in an example
• [N/A] New features and API changes have release notes
• [N/A] Documentation complies with general and docstring guidelines