[clang] [analyzer] Fix crash of StreamChecker when eval calling 'fopen' (PR #100990)

[Donát Nagy via cfe-commits]

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@@ -1703,7 +1703,11 @@ are detected:
 * Invalid 3rd ("``whence``") argument to ``fseek``.
 
 The stream operations are by this checker usually split into two cases, a success
-and a failure case. However, in the case of write operations (like ``fwrite``,
+and a failure case.
+On the success case it also assumes that the current value of ``stdout``,
+``stderr``, or ``stdin`` can't be equal to the file pointer returned by ``fopen``.
+
+In the case of write operations (like ``fwrite``,
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NagyDonat wrote:

Ok, then feel free to keep the short diff.

https://github.com/llvm/llvm-project/pull/100990