Expunge read-with-symbol-position and read-symbol-positions-list

Expunge read-with-symbol-position and read-symbol-positions-list

These are remnants of the old way of determining byte compiler warning
positions.

* src/lread.c (read_internal_start, read1): Remove initializations amd
manipulations of these variables.
(syms_of_lread): Remove the declarations of the variables.

* lisp/emacs-list/bytecomp.el (compile-defun, byte-compile-from-buffer):
Remove bindings of the variables.