read: fix #e after #x

Corrects a bug in 0549bfb1e5 where `#x` causes the `e` in `#e` to be
interpreted as 14 instead of the character `#\e`.

pkgs/racket-test-core/tests/racket/numstrs.rktl

@@ -132,7 +132,12 @@
     (5000.0 "1#/2#e4")
     (500000000.0 "1/2#e10")
     (500000000 "#e1/2#e10")
+    (36 "#e#x24")
+    (-36 "#e#x-24")
+    (36 "#x#e24")
+    (-36 "#x#e-24")
     (16140901064495857664-50176i "#e#x+e#s+e@-e#l-e")
+    (16140901064495857664-50176i "#x#e+e#s+e@-e#l-e")
 
     (,(make-rectangular -inf.f 3.1415927f0) "-inf.f+3.1415927f0i")
     (,(make-rectangular -inf.0 3.1415927) "-inf.f+3.1415927i")

racket/src/expander/read/number.rkt

@@ -434,7 +434,8 @@
    [(#\#)
     (define next (fx+ 1 start))
     (parse-case
-     s next end radix => i
+     ;; use `10` instead of `radix`, because we don't want a hex conversion
+     s next end 10 => i
      [(eof)
       (fail convert-mode "no character after `#` indicator in `~.a`" s)]
      [(#\e #\E #\i #\I)

racket/src/racket/src/startup.inc

@@ -54680,8 +54680,7 @@ static const char *startup_source =
 "(let-values(((i_0)"
 "(if(fx= next_0 end_0)"
 " 'eof"
-"(let-values(((c_1)(string-ref s_0 next_0)))"
-"(maybe-digit c_1 radix_0)))))"
+"(let-values(((c_1)(string-ref s_0 next_0)))(maybe-digit c_1 10)))))"
 "(if(let-values(((or-part_0)(eqv? i_0 'eof)))(if or-part_0 or-part_0 #f))"
 "(let-values()"
 "(if(eq?(state->convert-mode convert-mode_0) 'must-read)"