Undo param.h pollution to fix build with boost >= 1.87

Index: src/libslic3r/Platform.cpp
--- src/libslic3r/Platform.cpp.orig
+++ src/libslic3r/Platform.cpp
@@ -13,6 +13,10 @@
 #include <mach/machine.h>
 #endif
 
+#if defined(OpenBSD)
+#undef OpenBSD
+#endif
+
 namespace Slic3r {
 
 static auto s_platform 		  = Platform::Uninitialized;
