fixes in debug drawer: always use rgba color with each component in range [0..1]

use sphere/box rendering of debug drawer
Thanks accodejockey for the report: See http://code.google.com/p/bullet/issues/detail?id=280
Also see http://code.google.com/p/bullet/issues/detail?id=279

Demos/OpenGL/RenderTexture.h

@@ -33,6 +33,7 @@ public:
 	renderTexture(int width,int height);
 	~renderTexture();
 
+	///rgba input is in range [0..1] for each component
 	inline void	setPixel(int x,int y,const btVector4& rgba)
 	{
 		unsigned char* pixel = &m_buffer[ (x+y*m_width) * 4];