BOOST_PP_REMOVE_PARENS() is dangerously broken -- it strips initial group of parentheses instead of surrounding

https://godbolt.org/z/38jbTP7qn

```
#include

int main(int argc, char *argv[]) {
#if MACRO
return BOOST_PP_REMOVE_PARENS((*argv)[1]); // Crash
#else
return (*argv)[1] ; // OK
#endif
}
```

Note the documentation piles extra confusion on top of this. It says:

> The `BOOST_PP_REMOVE_PARENS` macro removes the beginning parenthesis, if it exists, from the input data and expands to the result

"Parenthes**i**s" is singular (plural is parenthes**es**), so the documentation is claiming that only a beginning `(` is being removed. It makes no mention of removing any closing `)`, regardless of its expected location, even though the function apparently does that regardless of its location.

This is a massive pitfall. The name `BOOST_PP_REMOVE_PARENS` itself (and the intended usage) are misleading for most users and very unlikely to be what they actually want.

I would suggest, at the very least, renaming the macro to something like `BOOST_PP_REMOVE_BEGINNING_PARENS` and updating the documentation to clarify it is not doing what users would expect from a `REMOVE_PARENS` macro.

Start with the Godbolt reproducer and boost/preprocessor/punctuation/remove_parens.hpp to verify how BOOST_PP_REMOVE_PARENS handles the input. Review the documented contract and determine the intended API change, including compatibility and naming implications. Done means the behavior and documentation agree with an explicitly decided contract, with the reproducer no longer exposing the reported pitfall.

索引モデルが issue の本文から書いたものです。