reader: fix readtable and docs to match old protocol

Author: mflatt

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

@@ -150,7 +150,7 @@ already-consumed character(s): the source name, a line number or
 @racket[#f]. When the reader macro is triggered by @racket[read] (or
 @racket[read/recursive]), the procedure is passed only two arguments
 if it accepts two arguments, otherwise it is passed six arguments
-where the last four are all @racket[#f]. See @secref["reader-procs"]
+where the third is always @racket[#f]. See @secref["reader-procs"]
 for information on the procedure's results.
 
 A reader macro normally reads characters from the given input port to

racket/src/expander/read/readtable.rkt

@@ -161,7 +161,7 @@
       (parameterize ([current-read-config config])
         (if (procedure-arity-includes? handler 2)
             (handler c in)
-            (handler c in #f #f #f #f)))]
+            (handler c in #f line col pos)))]
      [else
       (parameterize ([current-read-config config])
         (handler c in (read-config-source config) line col pos))]))

racket/src/racket/src/startup.inc

@@ -46628,7 +46628,7 @@ static const char *startup_source =
 "(let-values()"
 "(if(procedure-arity-includes? handler_0 2)"
 "(handler_0 c_59 in_3)"
-"(handler_0 c_59 in_3 #f #f #f #f)))))"
+"(handler_0 c_59 in_3 #f line_3 col_2 pos_106)))))"
 "(let-values()"
 "(with-continuation-mark"
 " parameterization-key"