make headers work in C++

add two more variable length integer encoding functions

errmsg.h

@@ -5,6 +5,10 @@
 /* for exit(): */
 #include <stdlib.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /* These use file descriptor 2, not buffer_2!
  * Call buffer_flush(buffer_2) before calling these! */
 
@@ -27,4 +31,8 @@ void errmsg_infosys(const char* message, ...);
 #define msg(...) errmsg_info(__VA_ARGS__,(char*)0);
 #define msgsys(...) errmsg_infosys(__VA_ARGS__,(char*)0);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif