Unescape the characters in a string. In strunescape syntax, str is an input string, escapedCharsStr is a string of chars to unescape when found in str, and escapeStr is a one character string that is used as the escape character.
returnedString = strunescape(str, escapedCharsStr, escapeStr)
returnedString - type: str
str - type: str
escapedCharsStr - type: str
escapeStr - type: str
Unescaping removes the escape char preceding each instance of the escaped chars.