cswriter: do not print a useless warning when input is JSON

If someone uses a plain-text format, they cannot really expect scan
properties to be preserved.

Author: kdudka

src/cswriter.cc

@@ -100,3 +100,8 @@ void CovWriter::flush()
 {
     d->str.flush();
 }
+
+// only to prevent AbstractWriter::setScanProps() from printing a warning
+void CovWriter::setScanProps(const TScanProps &)
+{
+}

src/cswriter.hh

@@ -29,6 +29,7 @@ class CovWriter: public AbstractWriter {
 
         virtual void handleDef(const Defect &def);
         virtual void flush();
+        virtual void setScanProps(const TScanProps &);
 
     private:
         struct Private;