Added extern "C" if __cplusplus is defined.

diff --git a/include/ddeml.h b/include/ddeml.h
index 284c636..ec147ed 100644
--- a/include/ddeml.h
+++ b/include/ddeml.h
@@ -10,6 +10,10 @@
 
 #include "windef.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif /* defined(__cplusplus) */
+
 /* Codepage Constants
  */
 
@@ -334,4 +338,8 @@
 UINT16    WINAPI DdeQueryConvInfo16(HCONV,DWORD,LPCONVINFO16);
 UINT      WINAPI DdeQueryConvInfo(HCONV,DWORD,LPCONVINFO);
 
+#ifdef __cplusplus
+} /* extern "C" */
+#endif /* defined(__cplusplus) */
+
 #endif  /* __WINE__DDEML_H */