* lisp/emacs-lisp/testcover.el: Don't use edebug--read (bug#20487)

* lisp/emacs-lisp/testcover.el: Don't use edebug--read (bug#20487)

* lisp/emacs-lisp/testcover.el: Use lexical-binding.
(testcover--read): Rename from testcover-read.  Change calling convention.
Use edebug-read-and-maybe-wrap-form now that edebug-read is gone.
(testcover-start): Use add-function.  Move edebug-all-defs binding to
testcover--read.
(testcover-this-defun): Tighten scope of edebug-all-defs binding.
(testcover-mark): Remove unused var `item'.

* src/lread.c (syms_of_lread): Default load-read-function to `read'.