print debug info about fb's line_length
fix size error when mmapping and mallocing buffers

We used to calculate the size of buffers by multipling the xres and
yres, but there is a field in global_fix_screen_info indicating the real
length of the framebuffer.
Merge branch 'fix1366'

Now we use a more correct way to write data into buffers, utilizing more
data from global_fix_screen_info. The server should now be compatible
with screens with a width of 1366 pixels, no matter what the line_length
of the framebuffer is. Actually I think even more screens should also be
supported.

But this doesn't mean the problem with framebuffer is fully solved.
remove debug output in cursor.c