Add wxAffineMatrix2D and related classes.

This class represents an affine 2D transformation and will be used in wxDC for
now and maybe in wxGC later.

Closes #13143.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67520 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/wx/affinematrix2dbase.h

@@ -0,0 +1,34 @@
+/////////////////////////////////////////////////////////////////////////////
+// Name:        affinematrix2dbase.h
+// Purpose:     wxMatrix2D documentation
+// Author:      wxWidgets team
+// Licence:     wxWindows licence
+/////////////////////////////////////////////////////////////////////////////
+
+/**
+    @class wxMatrix2D
+
+    A simple container for 2x2 matrix.
+
+    This simple structure is used with wxAffineMatrix2D.
+
+    @library{wxcore}
+    @category{misc}
+
+    @since 2.9.2
+ */
+struct wxMatrix2D
+{
+    /**
+        Default constructor.
+
+        Initializes the matrix elements to the identity.
+     */
+    wxMatrix2D(wxDouble v11 = 1,
+               wxDouble v12 = 0,
+               wxDouble v21 = 0,
+               wxDouble v22 = 1);
+
+    /// The matrix elements in the usual mathematical notation.
+    wxDouble m_11, m_12, m_21, m_22;
+};