* include/ipexport.h: Add missing `extern "C"' directives.

* include/iphlpapi.h: Ditto.
        * include/iprtrmib.h: Ditto.
        * include/iptypes.h: Ditto.

winsup/w32api/include/iprtrmib.h

@@ -3,6 +3,10 @@
 
 #include <ipifcons.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #ifndef ANY_SIZE
 #define ANY_SIZE 1
 #endif
@@ -223,4 +227,8 @@ typedef struct {
   MIB_UDPROW table[ANY_SIZE];
 } MIB_UDPTABLE, *PMIB_UDPTABLE;
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* _IPRTRMIB_H_ */