add wxImage::Clear (patch by troelsk); closes #10141

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@57946 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/image.h

@@ -240,6 +240,9 @@ public:
     bool Create( char** xpmData ) { return Create(const_cast<const char* const*>(xpmData)); }
 #endif
     void Destroy();
+   
+    // initialize the image data with zeroes
+    void Clear(unsigned char value = 0);
 
     // creates an identical copy of the image (the = operator
     // just raises the ref count)