Fix unescaping in rexx, skew, vimscript

rexx/reader.rexx

@@ -95,9 +95,10 @@ is_number: procedure /* is_number(token) */
 parse_string: procedure /* parse_string(token) */
   token = arg(1)
   res = substr(token, 2, length(token) - 2) /* Remove quotes */
+  res = changestr("\\", res, '01'x)
   res = changestr("\n", res, '0A'x)
   res = changestr('\"', res, '"')
-  res = changestr("\\", res, '5C'x)
+  res = changestr('01'x, res, '5C'x)
   return res
 
 parse_keyword: procedure /* parse_keyword(token) */

skew/reader.sk

@@ -30,7 +30,7 @@ def tokenize(str string) List<string> {
 }
 
 def unescape(s string) string {
-  return s.replaceAll("\\\"", "\"").replaceAll("\\n", "\n").replaceAll("\\\\", "\\")
+  return s.replaceAll("\\\\", "\x01").replaceAll("\\\"", "\"").replaceAll("\\n", "\n").replaceAll("\x01", "\\")
 }
 
 def read_atom(rdr Reader) MalVal {

vimscript/reader.vim

@@ -42,12 +42,20 @@ function Tokenize(str)
   return tokens
 endfunction
 
+function UnescapeChar(seq)
+  if a:seq == '\"'
+    return '"'
+  elseif a:seq == '\n'
+    return "\n"
+  elseif a:seq == '\\'
+    return '\'
+  else
+    return a:seq
+  endif
+endfunction
+
 function ParseString(token)
-  let str = a:token[1:-2]
+  return substitute(a:token[1:-2], '\\.', '\=UnescapeChar(submatch(0))', "g")
-  let str = substitute(str, '\\"', '"', "g")
-  let str = substitute(str, '\\n', "\n", "g")
-  let str = substitute(str, '\\\\', "\\", "g")
-  return str
 endfunction
 
 function ReadAtom(rdr)