The in_poly function is already declared in lib/pathplan/pathutil.h.
Without this change, an upcoming commit that adds dllimport/dllexport
storage-class attribute declarations in lib/pathplan/pathutil.h would
cause the following warning for the duplicate definition:
C:\Users\magja\graphviz\lib\neatogen\neatosplines.c(27,48): warning C4273: 'in_poly': inconsistent dll linkage [C:\Users\magja\graphviz\build\lib\neatogen\neatogen.vcxproj]
Towards https://gitlab.com/graphviz/graphviz/-/issues/2058.
#include <ortho/ortho.h>
#endif
-extern int in_poly(Ppoly_t argpoly, Ppoint_t q);
-
static boolean spline_merge(node_t * n)
{