Sdl_getkeystate was not declared in this scope

I have downloaded the SDL (Developement Libraries For Mingw) and I set it up with codeblocks.
I am doing all of this because I have downloaded the source Code for a game that uses SDL ( I want to study the code to see how it works. However I can’t get it to compile, it gives me a lot of ‘not declared in this scope’ errors. The first one is "sdl_getkeystate was not declared in this scope’. I don’t know why. I have included the SDL.h header like it says in the documentation but it just compile, I have googled around quite a bit with no luck.
Any help would be much appreciated.

Thank You.