Several amendments to scratch/correct-warning-pos.

The position return by read-positioning-symbols is now the position in the
buffer, rather than the offset from the start of a form, enabling warning
positions in other parts of the buffer to be output.

* src/lisp.h (lisp_h_EQ): Add XLI casts so that it compiles cleanly.

* src/data.c (Fremove_pos_from_symbol): New DEFUN.

* src/lread.c (readchar_count): renamed to readchar_offset.
(read_internal_start) Initialize readchar_offset to the buffer's point when
STREAM is a buffer.

* lisp/emacs-lisp/bytecomp.el (byte-compile-warning-prefix): Amend to use
OFFSET as a buffer position, not an offset from the start of a form.
(byte-compile-warn): Remove symbol positions from any shape of ARGS, not just
a symbol with position.

* lisp/emacs-lisp/cconv.c (cconv-convert): In the :unused case, position the
new IGNORE symbol with the VAR it has replaced.

* lisp/emacs-lisp/macroexp.el (macroexp--warn-wrap, macroexp-warn-and-return):
Add an extra position parameter to each.

* lisp/emacs-lisp/bindat.el (bindat-type), lisp/emacs-lisp/byte-run.el
(defmacro, defun), lisp/emacs-lisp/cconv.el (cconv--convert-func-body)
(cconv-convert), lisp/emacs-lisp/cl-generic.el (cl-defmethod),
lisp/emacs-lisp/cl-macs.el (cl-symbol-macrolet, cl-defstruct),
lisp/emacs-lisp/easy-mmode.el (define-minor-mode),
lisp/emacs-lisp/eieio-core.el (eieio-oref, eieio-oref-default)
(eieio-oset-default), lisp/emacs-lisp/eieio.el (defclass),
lisp/emacs-lisp/gv.el (gv-ref), lisp/emacs-lisp/macroexp.el
(macroexp-macroexpand, macroexp--unfold-lambda, macroexp--expand-all),
lisp/emacs-lisp/pcase.el (pcase-compile-patterns, pcase--u1): Add an extra
position argument to each call of macroexp-warn-and-return.

lisp/emacs-lisp/pcase.el

@@ -433,6 +433,7 @@ how many time this CODEGEN is called."
                     (memq (car case) pcase--dontwarn-upats))
           (setq main
                 (macroexp-warn-and-return
+                 (car case)
                  (format "pcase pattern %S shadowed by previous pcase pattern"
                          (car case))
                  main))))
@@ -940,7 +941,7 @@ Otherwise, it defers to REST which is a list of branches of the form
         (let ((code (pcase--u1 matches code vars rest)))
           (if (eq upat '_) code
             (macroexp-warn-and-return
-             ;; upat
+             upat
              "Pattern t is deprecated.  Use `_' instead"
              code))))
        ((eq upat 'pcase--dontcare) :pcase--dontcare)