dumplots can just take a reference

src/dccutil.cc

@@ -217,7 +217,7 @@ colorbuf(char *buf, size_t len, int idx, size_t bufsiz)
 
 /* Dump a potentially super-long string of text.
  */
-void dumplots(int idx, const char *prefix, const bd::String data)
+void dumplots(int idx, const char *prefix, const bd::String& data)
 {
   if (unlikely(!*data)) {
     dprintf(idx, "%s\n", prefix);

src/dccutil.h

@@ -37,7 +37,7 @@ namespace bd {
 
 
 void init_dcc(void);
-void dumplots(int, const char *, bd::String);
+void dumplots(int, const char *, const bd::String&);
 void rdprintf(const char*, int, const char *, ...) __attribute__((format(printf, 3, 4)));
 void dprintf(int, const char *, ...) __attribute__((format(printf, 2, 3)));
 void dprintf_real(int, char*, size_t, size_t, const char* = NULL);