configure: Check for a different SDL function

This one is available both in SDL 1.2 and in 1.3 (which is the current
version available e.g. in macports), while 1.3 doesn't contain
SDL_Linked_Version().

The current check for SDL_Linked_Version() (available since SDL 1.2.13)
was added in 8f1b06c8, because including the headers for SDL_Init()
redirects the main() function, requiring the main function signature
to match the one of SDL_main (including argc/argv).

Signed-off-by: Martin Storsjö <martin@martin.st>
