coreinit/thread: OSThreadEntryPointFn and OSCreateThread take void* for arg

[capitalistspz]

There's no reason for OSThreadEntryPointFn to take const char** when argv uses the value that is char* in OSCreateThread, there's also no reason for params to be char related when they're not type restricted

[GaryOderNichts]

I'm unsure about this PR. The char* obviously doesn't make sense, but changing the signature of OSThreadEntryPointFn would raise compiler errors on all existing projects.

[capitalistspz]

Better to break them now than later or never, and it at least doesn't cause any logic errors