[SDL] SDL 1.3 and rendering API state management

[Simon]

> Why not do it properly while we're at it? Unless there is a clean way 
> of getting "normal" SDL code to play along with code using OpenGL or 
> Direct3D directly, we're not really improving the situation much 
> compared to SDL 1.2.

I agree, right now I feel as if the library would "behave" correctly 
with other library, until the developer decide they don't anymore and 
start mixing render context and so on.  But this is to be expected. 
There must be a way inside SDL to "regulate" the use of extra libraries. 
  Right now it seems to be an almost perfect free-for-all.

I suggest leaving all this in the hands of the developer, give him a big 
warning that doing this and that can result in such kinds of problems, 
but of course, provide this developer with tools to assist him in making 
sure the problems never happen in production.  I'm thinking about a way 
to monitor the state changes and a convenient way to deal with them 
(change them back, save state/restore state, etc...)

And besides, if new functionality is given to us to the price of some 
complication, I'm sure this is a deal some of us can agree with! ;)

Good luck,
   Simon