rasterfont 为内部函数，BRUSH 结构体增加 maskc 和 alpha 字段，去掉 pixellwsalpha
调整目录结构，实现 maskalpha 的 scanline
bug fix for color mask & alpha blending scanline fill
implements match pal function & many bug fixes
1. fix bmp load & save bug in bmpfile.c
2. when create 256-color bmp, use stdpal for default
3. implements match palette function
4. modify win.c for stdpal create
bitblt & bug fixs
1. add bitblt module, implements bitblt & putbmp functions
2. fix bugs in match palette