Fixed all issues detected by the test cases under MinGW - such as usage of abs() -> changed to qAbs(), rounding issues detected during calculations, and changed streaming methods with qDebug() (QDebug vs &QDebug issue).

src/blackmisc/mathematics.h

@@ -70,6 +70,16 @@ public:
      */
     static double roundEpsilon(double value, double epsilon);
 
+    /*!
+     * \brief PI
+     * \return
+     */
+    static const double &PIHALF()
+    {
+        static double pi = 2.0 * qAtan(1.0);
+        return pi;
+    }
+
     /*!
      * \brief PI
      * \return
@@ -86,7 +96,7 @@ public:
      */
     static const double &PI2()
     {
-        static double pi2 = PI();
+        static double pi2 = 8.0 * qAtan(1.0);
         return pi2;
     }