A dozen unused return value warnings

[Daniel J S. <dan...@ie...>]

On my system, configuration results in the unused return variable flag 
being set.  Attached is a diff file with code changes to get rid of 
those warnings.

One in particular I have a question about:

diff -u -r1.6 QtGnuplotApplication.cpp
--- src/qtterminal/QtGnuplotApplication.cpp	29 Jan 2014 15:48:51 -0000	1.6
+++ src/qtterminal/QtGnuplotApplication.cpp	29 Mar 2017 18:47:43 -0000
@@ -80,8 +80,8 @@
  	// Some programs executing gnuplot -persist may be waiting for all 
default
  	// handles to be closed before they consider the sub-process finished.
  	// Using freopen() ensures that debug fprintf()s won't crash.
-	freopen("/dev/null","w",stdout);
-	freopen("/dev/null","w",stderr);
+	if (freopen("/dev/null","w",stdout));
+	if (freopen("/dev/null","w",stderr));
  }

Should the above really be included in Qt?  I don't think that Qt C++ 
files need to use FPRINTF() any more for debugging.  Qt has it's own 
messaging system:

http://doc.qt.io/qt-4.8/debug.html

qDebug(), qWarning(), qCritical(), qFatal().

Dan