dynapi: Optionally log every call into the SDL API. This will only log things going through dynapi, which means it won't do anything if dynapi is disabled for a given build, but also things that call the `*_REAL` version of an API won't log either (which is to say, if an internal piece of SDL calls a public API, it won't log it, but if an application calls that same entry point, it will). Since this just inserts a different function pointer, unless you explicitly request this at runtime, it won't add any overhead, and, of course, the entire thing can be turned off with a single #define so it doesn't even add extra unused code to the shared library if the kill switch is flipped.