Use '$' to escape special characters in all ports

Before, Power and S390 used '.' as escape character, for no apparent reason.

Remove the "escape char" parameter from Emitaux.emit_symbol.
Instead, '$' is "hard-wired" as the escape char.

Author: xavierleroy

Diff for: asmcomp/arm/emit.mlp

@@ -31,10 +31,7 @@ open Emitenv
 let emit_label lbl =
   emit_string ".L"; emit_int lbl
 
-(* Symbols *)
-
-let emit_symbol s =
-  Emitaux.emit_symbol '$' s
+(* Calls and tail calls *)
 
 let emit_call s =
   if !Clflags.dlcode || !Clflags.pic_code

Diff for: asmcomp/arm64/emit.mlp

@@ -49,7 +49,7 @@ let emit_label lbl =
 
 let emit_symbol s =
   if macosx then emit_string "_";
-  Emitaux.emit_symbol '$' s
+  Emitaux.emit_symbol s
 
 (* Object types *)
 

Diff for: asmcomp/emitaux.ml

@@ -35,14 +35,14 @@ let emit_printf fmt =
 
 let emit_int32 n = emit_printf "0x%lx" n
 
-let emit_symbol esc s =
+let emit_symbol s =
   for i = 0 to String.length s - 1 do
     let c = s.[i] in
     match c with
       'A'..'Z' | 'a'..'z' | '0'..'9' | '_' ->
         output_char !output_channel c
     | _ ->
-        Printf.fprintf !output_channel "%c%02x" esc (Char.code c)
+        Printf.fprintf !output_channel "$%02x" (Char.code c)
   done
 
 let emit_string_literal s =

Diff for: asmcomp/emitaux.mli

@@ -20,7 +20,7 @@ val emit_string: string -> unit
 val emit_int: int -> unit
 val emit_nativeint: nativeint -> unit
 val emit_int32: int32 -> unit
-val emit_symbol: char -> string -> unit
+val emit_symbol: string -> unit
 val emit_printf: ('a, out_channel, unit) format -> 'a
 val emit_char: char -> unit
 val emit_string_literal: string -> unit

Diff for: asmcomp/power/emit.mlp

@@ -75,10 +75,6 @@ let (trap_size, trap_handler_offset, trap_previous_offset) =
   | ELF64v1 -> (32, 56, 64)
   | ELF64v2 -> (32, 40, 48)
 
-(* Output a symbol *)
-
-let emit_symbol s = Emitaux.emit_symbol '.' s
-
 (* Output a label *)
 
 let label_prefix = ".L"

Diff for: asmcomp/s390x/emit.mlp

@@ -44,10 +44,6 @@ let slot_offset env loc cls =
   | Outgoing n -> n
   | Domainstate _ -> assert false  (* not a stack slot *)
 
-(* Output a symbol *)
-
-let emit_symbol s = Emitaux.emit_symbol '.' s
-
 (* Output function call *)
 
 let emit_call s =