Remove duplicate declarations of background in Menu subclasses
Clean up SDLRenderDevice

* Add screen and titlebar_icon to SDLRenderDevice init list
* Reduce scope of some variables in scaleSurface()
Move tip_buffer to init list of TooltipData copy constructor
Remove unused alpha functions from SDL_gfxBlitFunc
Merge pull request #933 from dorkster/static_analysis

Fix some bugs found by cppcheck