[libcxx-commits] [libcxx] [libc++][NFC] Rearrange functions in the synopsis comments of `<cmath>` (PR #100862)

[via libcxx-commits]

PaulXiCao wrote:

The previous order was (almost?) an exact copy of the standard I believe (e.g. see https://eel.is/c++draft/c.math.syn). I see benefits to sticking to that order instead of defining a new one which might not be adhered to by new contributors.

Nonetheless, there are things to update, e.g. 
```cpp
//
// from main
// 
floating_point hypot (arithmetic x, arithmetic y);
float          hypotf(float x, float y);
long double    hypotl(long double x, long double y);

double       hypot(double x, double y, double z);                // C++17
float        hypot(float x, float y, float z);                   // C++17
long double  hypot(long double x, long double y, long double z); // C++17

//
// from the standard
//
constexpr floating-point-type hypot(floating-point-type x, floating-point-type y);
constexpr float hypotf(float x, float y);
constexpr long double hypotl(long double x, long double y);

// [[c.math.hypot3]](https://eel.is/c++draft/c.math.hypot3), three-dimensional hypotenuse
constexpr floating-point-type hypot(floating-point-type x, floating-point-type y,
                                    floating-point-type z);
```
I would also include `constexpr` as long as we support it.

I do not have an opinion yet what to do about the comments and links therein (e.g. `// [[c.math.hypot3]](https://eel.is/c++draft/c.math.hypot3), three-dimensional hypotenuse`). Not sure if there is really a benefit if we also include those.

https://github.com/llvm/llvm-project/pull/100862