MATH: Add workaround for MSVC 2015 compiler bug (C2248)

At least MSVC 2015 (14.0.25420.01 Update 3) will hit a C2248 compiler
error.  Quoting @lephilousophe, "It looks like a bug. It tries to
generate a move constructor but it believes it can't access the base
constructor, although the constructor it creates is in a child class,
while the MatrixBase constructor is protected."

Since MSVC 2015 is still able to compile most of the engines and
components (not all of them, though), having a local hack for it
seems reasonable...

math/matrix.h

@@ -142,12 +142,17 @@ public:
 	Matrix<rows, cols> &operator/=(float factor);
 	Matrix<rows, cols> &operator/=(const Matrix<rows, cols> &m);
 
+#if defined(_MSC_VER) && _MSC_VER < 1910 // HACK: C2248 bug in MSVC 2015
+public:
+#else
 protected:
+#endif
 	constexpr MatrixBase() = default;
 	MatrixBase(const float *data);
 	MatrixBase(const MatrixBase<rows, cols> &m);
 	MatrixBase &operator=(const MatrixBase<rows, cols> &m);
 
+protected:
 	inline const Matrix<rows, cols> &getThis() const {
 		return *static_cast<const Matrix<rows, cols> *>(this); }
 	inline Matrix<rows, cols> &getThis() {
@@ -163,7 +168,11 @@ private:
  */
 template<int r, int c>
 class MatrixType : public MatrixBase<r, c> {
+#if defined(_MSC_VER) && _MSC_VER < 1910 // HACK: C2248 bug in MSVC 2015
+public:
+#else
 protected:
+#endif
 	constexpr MatrixType() : MatrixBase<r, c>() { }
 	MatrixType(const float *data) : MatrixBase<r, c>(data) { }
 	MatrixType(const MatrixBase<r, c> &m) : MatrixBase<r, c>(m) { }

math/vector.h

@@ -57,7 +57,11 @@ public:
 	 */
 	void readFromStream(Common::ReadStream *stream);
 
+#if defined(_MSC_VER) && _MSC_VER < 1910 // HACK: C2248 bug in MSVC 2015
+public:
+#else
 protected:
+#endif
 	MatrixType() : MatrixBase<dim, 1>() { }
 	MatrixType(const float *data) : MatrixBase<dim, 1>(data) { }
 	MatrixType(const MatrixBase<dim, 1> &m) : MatrixBase<dim, 1>(m) { }