fix ocamllex -ml, works with -safe-string option (ocaml#750)

Author: bobzhang

Changes

@@ -166,6 +166,9 @@ OCaml 4.04.0:
 
 ### Tools:
 
+- MPR#7323: ocamllex -ml work with (-safe-string)
+ (Hongbo Zhang)
+ 
 - MPR#7189: toplevel #show, follow chains of module aliases
  (Gabriel Scherer, report by Daniel Bünzli, review by Thomas Refis)
 

lex/outputbis.ml

@@ -44,7 +44,7 @@ let output_auto_defs oc has_refill =
 \n end\
 \n end else begin\
 \n let i = lexbuf.Lexing.lex_curr_pos in\
-\n let c = lexbuf.Lexing.lex_buffer.[i] in\
+\n let c = Bytes.get lexbuf.Lexing.lex_buffer i in\
 \n lexbuf.Lexing.lex_curr_pos <- i+1 ;\
 \n state lexbuf k (Char.code c)\
 \n end\
@@ -61,7 +61,7 @@ let output_auto_defs oc has_refill =
 \n end\
 \n end else begin\
 \n let i = lexbuf.Lexing.lex_curr_pos in\
-\n let c = lexbuf.Lexing.lex_buffer.[i] in\
+\n let c = Bytes.get lexbuf.Lexing.lex_buffer i in\
 \n lexbuf.Lexing.lex_curr_pos <- i+1 ;\
 \n Char.code c\
 \n end\