Correct search string for variables name

To extract the goals variables values from the output dataset,
Qucs writes some files in the extract/ directory defining, among other
things, the text string to search in the dataset to locate the variable.
ASCO does a SUBstring match, so the search string need also to contain
the string delimiter (a trailing space), otherwise it will match any
ither string starting with the same characters.

qucs/qucs/components/opt_sim.cpp

@@ -183,7 +183,7 @@ bool Optimize_Sim::createASCOFiles()
 	stream << "#\n\n";
 	stream << "# Post Processing #\n";
 	stream << "MEASURE_VAR:#SYMBOL#:SEARCH_FOR:'<indep " << VarName
-	       << "':S_COL:01:P_LINE:01:P_COL:01:31" << "\n";
+	       << " ':S_COL:01:P_LINE:01:P_COL:01:31" << "\n";
 	stream << "#\n\n";
 	efile.close();
       }