line_trans

      from: <string>
      to: <string>

 This looks at the current line for characters in the from string and
 replaces them with the corresponding characters in the to string.

 eg:  line_trans "{}" "()"

 This converts all curly brackets to round brackets.

 Ranges of characters can be specified

 eg:  line_trans "A-Z" "a-z"

 This converts all uppercase letters to the corresponding lowercase
 letter. - needs a character before and after it. It should not be used
 at the beginning or the end of to of from.

 The - can be escaped to cancel its special meaning

 eg:  line_trans "\-" "+"

 This converts all minuses to plusses.

 For this function to work, the to and from strings must be the
 same length.