bug#64272: 28.1; lisp_file_lexically_bound_p behavior mismatches file local variables

[LdBeth <andpuke@foxmail.com>]

>>>>> In <tencent_801CA17A56314C746AAC30FFB8DC58BB1109@qq.com> 
>>>>>	LdBeth <andpuke@foxmail.com> wrote:

ldb> So as I continue digging into lread.c and trying to find alternative
ldb> solutions, I find these:

ldb>   DEFSYM (Qget_file_char, "get-file-char");

ldb>   /* Used instead of Qget_file_char while loading *.elc files compiled
ldb>      by Emacs 21 or older.  */
ldb>   DEFSYM (Qget_emacs_mule_file_char, "get-emacs-mule-file-char");

ldb> While `get-file-char` is exposed to emacs lisp,
ldb> `get-emacs-mule-file-char' is not even a defined lisp function.

ldb> There are multiple places in `lread.c` that handles
ldb> `Qget_emacs_mule_file_char`. Which I believe it time to consider
ldb> them as dead code and remove them.

Sorry, I misread on how `Qget_emacs_mule_file_char' is been used.
It is still been used internally in `lread.c' because of how READCHAR
works.

ldb> For the only two functions that calls `lisp_file_lexically_bound_p`,
ldb> `load` is hard coded to use `get-file-char` which is a wrapper around
ldb> `getc()`, and `eval-buffer` uses the `BUFFERP (readcharfun)`
ldb> branch in `readchar`. I think both case can be changed to
ldb> use a more flexible way to test file local variables
ldb> rather than stick to the READCHAR UNREAD api.

I think this still holds valid.

---
ldb