Add `extern "C"` to export in plugin/gdiplus

plugin/gdiplus is a C++ project, so the `extern "C"` must be added in
order to export C symbols that can be used by the rest of the code.

diff --git a/plugin/gdiplus/gvplugin_gdiplus.cpp b/plugin/gdiplus/gvplugin_gdiplus.cpp
index d645cf53b0461b588b05b1617113890a8231573d..efd3195789c10edd9c08465c401b95476e188dfc 100755 (executable)
--- a/plugin/gdiplus/gvplugin_gdiplus.cpp
+++ b/plugin/gdiplus/gvplugin_gdiplus.cpp
@@ -89,6 +89,10 @@ static gvplugin_api_t apis[] = {
     {(api_t)0, 0},
 };
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #ifdef _WIN32
 #   define GVPLUGIN_GDIPLUS_API __declspec(dllexport)
 #else
@@ -96,3 +100,7 @@ static gvplugin_api_t apis[] = {
 #endif
 
 GVPLUGIN_GDIPLUS_API gvplugin_library_t gvplugin_gdiplus_LTX_library = { "gdiplus", apis };
+
+#ifdef __cplusplus
+}
+#endif