[clang] [clang][analyzer] Model more getline/getdelim pre and postconditions (PR #83027)

[Alejandro Álvarez Ayllón via cfe-commits]

alejandro-alvarez-sonarsource wrote:

> : "If *n is non-zero, the application shall ensure that *lineptr either points to an object of size at least *n bytes, or is a null pointer."

Ah! I was following at the 2008 version, and there "[...], or is a null pointer." is missing. I will update accordingly. I wonder, though, if the pointer is NULL, would an undefined (as non-initialized) *n be acceptable?

https://github.com/llvm/llvm-project/pull/83027