Added mechanism for registering proxy objects in the .osg plugin in a way that is compatible with static linking.

src/osgPlugins/osg/Texture.cpp

@@ -25,7 +25,7 @@ bool Texture_matchSourceTypeStr(const char* str,int& value);
 const char* Texture_getSourceTypeStr(int value);
 
 // register the read and write functions with the osgDB::Registry.
-RegisterDotOsgWrapperProxy g_TextureProxy
+REGISTER_DOTOSGWRAPPER(Texture)
 (
     0,
     "TextureBase",