make headers work in C++

add two more variable length integer encoding functions

textcode.h

@@ -4,6 +4,10 @@
 
 #include <stddef.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /* These take len bytes from src and write them in encoded form to
  * dest (if dest != NULL), returning the number of bytes written. */
 
@@ -111,4 +115,8 @@ size_t scan_tofrom_array(size_t (*func)(const char*,char*,size_t*),
 
 extern const char base64[64];
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif