support osc 52 clipboard copy integration.

This feature is particularly relevant for mosh for chrome (which also
used in windows I believe).

src/terminal/terminaldispatcher.cc

@@ -42,6 +42,8 @@
 
 using namespace Terminal;
 
+static const size_t MAXIMUM_CLIPBOARD_SIZE = 16*1024;
+
 Dispatcher::Dispatcher()
   : params(), parsed_params(), parsed( false ), dispatch_chars(),
     OSC_string(), terminal_to_host()
@@ -235,7 +237,7 @@ void Dispatcher::dispatch( Function_Type type, const Parser::Action *act, Frameb
 void Dispatcher::OSC_put( const Parser::OSC_Put *act )
 {
   assert( act->char_present );
-  if ( OSC_string.size() < 256 ) { /* should be a long enough window title */
+  if ( OSC_string.size() < MAXIMUM_CLIPBOARD_SIZE) {
     OSC_string.push_back( act->ch );
   }
 }