0031189: Draw Harness, ViewerTest - send messages to Message::DefaultMessenger()

Added short-cuts methods in Message_Messenger for sending message with specified gravity,
and stream buffer class for using stream-like interface for that.
Similar short-cuts to DefaultMessenger() are added in Message package.

ViewerTest has been updated to send messages to Message::DefaultMessenger()
instead of direct output to std::cout/std::cerr.

Off-topic: spelling error (duplicate "and") is corrected in two places

Added test bugs fclasses bug31189

src/OSD/OSD_Parallel.cxx

@@ -140,7 +140,7 @@ namespace {
         return aCpuMask;
       }
 
-      // if we're not at the end of the item, expect a dash and and integer; extract end value.
+      // if we're not at the end of the item, expect a dash and integer; extract end value.
       int anIndexUpper = anIndexLower;
       if (aCharIter < aChunkEnd && *aCharIter == '-')
       {