need COREAPI_VERSION in p3d_plugin_config.h too

makepanda/makepanda.py

@@ -1492,6 +1492,7 @@ def WriteConfigSettings():
         plugin_config["P3D_PLUGIN_LOG_BASENAME3"] = ""
         plugin_config["P3D_PLUGIN_P3D_PLUGIN"] = ""
         plugin_config["P3D_PLUGIN_P3DPYTHON"] = ""
+        plugin_config["P3D_COREAPI_VERSION_STR"] = COREAPI_VERSION
 
     if (RUNTIME):
         dtool_config["HAVE_P3D_PLUGIN"] = '1'