File gcc-8-compile-fix.patch of Package mingw64-kdiagram

--- a/src/KChart/KChartMath_p.h   2019-07-23 18:45:37.505609010 +0000
+++ b/src/KChart/KChartMath_p.h   2019-07-23 18:45:44.169667906 +0000
@@ -47,7 +47,7 @@
 // We use our own ISNAN / ISINF in the code to detect
 // that we defined them.
 // reason: Windows does not have isnan() / isinf()
-#if defined (Q_OS_WIN)
+#if defined (_Q_OS_WIN)
 #include <float.h>
 #define ISNAN(x ) _isnan(x )
 #define ISINF(x ) (!(_finite(x ) + _isnan(x ) ) )