add and use racket/repl

As suggested by Sam: Using `racket/repl` to start a read-eval-print
loop can mean that less code is loaded if a startup language other
than `racket/base` is selected.

Closes #2064

pkgs/racket-doc/scribblings/reference/repl.scrbl

@@ -0,0 +1,12 @@
+#lang scribble/doc
+@(require "mz.rkt")
+
+@title[#:tag "repl-module"]{The @racketmodname[racket/repl] Library}
+
+@defmodule[racket/repl]
+
+The @racketmodname[racket/repl] provides the same
+@racket[read-eval-print-loop] binding as @racketmodname[racket/base], but
+with even fewer internal dependencies than @racketmodname[racket/base]. It is
+loaded in some situations on startup, as described in
+@secref["init-actions"].

pkgs/racket-doc/scribblings/reference/security.scrbl

@@ -18,4 +18,5 @@
 @include-section["code-inspectors.scrbl"]
 @include-section["plumbers.scrbl"]
 @include-section["sandbox.scrbl"]
+@include-section["repl.scrbl"]
 @include-section["linklet.scrbl"]

pkgs/racket-doc/scribblings/reference/startup.scrbl

@@ -80,20 +80,26 @@ submodule of the required module or the
 language is used before the module is instantiated; see
 @secref["configure-runtime"].
 
-After running all command-line expressions, files, and modules,
+After running all command-line expressions, files, and modules, Racket
-Racket or GRacket then starts a read-eval-print loop for interactive
+or GRacket then starts a read-eval-print loop for interactive
 evaluation if no command line flags are provided other than
-@tech{configuration options}.  If any command-line argument is
+@tech{configuration options}. For Racket, the read-eval-print loop is
+run by calling @racket[read-eval-print-loop] from
+@racketmodname[racket/repl]. For GRacket, the read-eval-print loop is
+run by calling @racket[graphical-read-eval-print-loop] from
+@racketmodname[racket/gui/base]. If any command-line argument is
 provided that is not a @tech{configuration option}, then the
 read-eval-print-loop is not started, unless the @Flag{i}/@DFlag{repl}
 flag is provided on the command line to
-specifically re-enable it. In addition, just before the command line
+specifically re-enable it.
+
+In addition, just before the read-eval-print loop
 is started, Racket runs @racketmodname[racket/interactive]
 and GRacket runs @racketmodname[racket/gui/interactive], unless a different
 interactive file is specified in the the installation's @filepath{config.rktd}
 file found in @racket[(find-config-dir)], or the file @filepath{interactive.rkt}
 is found in @racket[(find-system-path 'addon-dir)]. If the
-@Flag{q}/@DFlag{no-init-file} flag is specified on the command line
+@Flag{q}/@DFlag{no-init-file} flag is specified on the command line,
 then no interactive file is run.
 
 Finally, before Racket or GRacket exits, it calls the procedure that
@@ -103,7 +109,10 @@ specified. Requiring @racketmodname[racket/gui/base] sets this parameter call
 @racket[(racket 'yield)].
 
 @history[#:changed "6.7" @elem{Run @racketmodname[racket/interactive] file
-         rather than directly running @racket[(find-system-path 'init-file)].}]
+         rather than directly running @racket[(find-system-path 'init-file)].}
+         #:changed "6.90.0.30" @elem{Run a read-eval-print loop by
+         using @racketmodname[racket/repl] or @racketmodname[racket/gui/base]
+         instead of @racketmodname[racket/base] or @racketmodname[racket/gui/init].}]
 
 @; ----------------------------------------------------------------------
 

racket/collects/racket/private/misc.rkt

@@ -5,7 +5,7 @@
 (module misc '#%kernel
   (#%require "small-scheme.rkt" "define.rkt" "path.rkt" "old-path.rkt"
              "path-list.rkt" "executable-path.rkt"
-             "reading-param.rkt" "repl.rkt"
+             "reading-param.rkt" "../repl.rkt"
              (for-syntax '#%kernel "qq-and-or.rkt" "stx.rkt" "stxcase-scheme.rkt" "stxcase.rkt"))
   
   ;; -------------------------------------------------------------------------

racket/src/racket/main.c

@@ -482,13 +482,13 @@ static void do_scheme_rep(Scheme_Env *env, FinishArgs *fa)
 
 #ifdef GRAPHICAL_REPL
   if (!fa->a->alternate_rep) {
-    a[0] = scheme_intern_symbol("racket/gui/init");
+    a[0] = scheme_intern_symbol("racket/gui/base");
     a[1] = scheme_intern_symbol("graphical-read-eval-print-loop");
     ending_newline = 0;
   } else
 #endif
     {
-      a[0] = scheme_intern_symbol("racket/base");
+      a[0] = scheme_intern_symbol("racket/repl");
       a[1] = scheme_intern_symbol("read-eval-print-loop");
     }