Using CHANNEL_PRINTS to transfer printbuffers to stdout is now working.

luprex/cpp/core/printbuffer.hpp

@@ -149,6 +149,9 @@ public:
     // Reset the print channeler.
     void reset() { line_ = 0; }
     
+    // Check if there's anything to channel.
+    bool have_prints(const PrintBuffer *pb) const;
+
     // Copy any new lines from the printbuffer to the stream buffer.
     // Update the current line number.  Return true if the printbuffer
     // contains any lines that have already been channeled.