[AD] new blit

[Evert Glebbeek <eglebbk@xxxxxxxxxx>]

The attached patch against current new_api_branch moves the existing 
blitting functions over to the new api. In other words, what it does is to 
add

void al_blit(int flags, BITMAP *source, BITMAP *dest, int dest_x, int 
dest_y)
void al_blit_region(int flags, BITMAP *source, int source_x, int source_y, 
int source_w, int source_h, BITMAP *dest, int dest_x, int dest_y)
void al_blit_scaled(int flags, BITMAP *source, int source_x, int source_y, 
int source_w, int source_h, BITMAP *dest, int dest_x, int dest_y, int 
dest_w, int dest_h)

and move blit, masked_blit, stretch_blit, masked_stretch_blit and 
stretch_sprite over to the compatibility layer. What about draw_sprite? I 
know it uses different coed from masked_blit(), though it could really be 
considered a special case from that. What is the difference exactly? 
Should I special case it in the new blitting routines, or just use the 
more general masked_blit functionality?
This patch doesn't implement any new functionality, or even completely 
replace the old API, but it's a start. It probably needs quite some 
cleaning up first though.
I have a small problem though, I'm not sure I understand everything in the 
draft about clipping rectangles... as I read that, I had the impression 
that it's more complicated than it needs to be, or am I missing something?

Evert