qalc: Be silent if gnuplot is not detected

packages/qalc/libqalculate-Calculator.cc.patch

@@ -0,0 +1,12 @@
+diff -u -r ../libqalculate-2.0.0/libqalculate/Calculator.cc ./libqalculate/Calculator.cc
+--- ../libqalculate-2.0.0/libqalculate/Calculator.cc	2017-08-27 21:38:22.000000000 +0200
++++ ./libqalculate/Calculator.cc	2017-08-31 16:09:58.987236004 +0200
+@@ -9360,7 +9360,7 @@
+ 	char filename[MAX_PATH]; 
+ 	return SearchPath(NULL, "gnuplot", ".exe", MAX_PATH, filename, &lpFilePart);
+ #else
+-	FILE *pipe = popen("gnuplot -", "w");
++	FILE *pipe = popen("gnuplot - 2> /dev/null", "w");
+ 	if(!pipe) return false;
+ 	return pclose(pipe) == 0;
+ #endif