Make the effect of (defvar foo) local.

Make the effect of (defvar foo) local.
* src/eval.c (apply_lambda): Make static.  Remove eval_flag arg.
(Fsetq): Don't check declared_special.
(Fdefun, Fdefmacro): Use Ffunction.
(Fdefvar): Don't set declared_special for (defvar foo).
(FletX): Check locally-special vars.  Only do specbind once.
(Flet): Check locally-special vars.
(Feval): Don't check declared_special.
(funcall_lambda): Check locally-special vars.
* src/lisp.h (apply_lambda): Remove extern declaration.
* src/lread.c (readevalloop): CSE.
* lisp/subr.el (with-lexical-binding): Remove.