
Closes #132561. This is a check that rewrites `#if`s and `#elif`s like so: ```cpp #if defined(MEOW) // -> #ifdef MEOW #if !defined(MEOW) // -> #ifndef MEOW ``` And, since C23 and C++23: ```cpp #elif defined(MEOW) // -> #elifdef MEOW #elif !defined(MEOW) // -> #elifndef MEOW ```