添加鼠标程序，实现交互式画椭圆 在mfc 环境下实现-realize interactive ellipse

实现了椭圆界面的绘制，并且含有背景图片，完全基于MFC的应用程序-Ellipse drawn implements the interface and contains the background image, an application based solely on MFC

mfc 实现绘图功能的程序，基于单文档，能够实现线型选择，可以画矩形，椭圆，等等，还可以改变字体的大小。-MFC realize drawing function of the program, based on single document, will be able to realize the linear to choose, can draw rectangular, ellipse,, and so on, can also change the font size.

例2-5 在屏幕客户区内绘制内切椭圆，椭圆的形状依据客户区形状而改变。椭圆边界为1像素宽的蓝线，内部填充为绿色(Example 2-5 draws an inscribed ellipse in the screen client area, and the shape of the ellipse varies according to the shape of the client area. The ellipse boundary is 1 pixels wide blue line,