Escapes the special characters '\b', '\f', '\n', '\r', '\t', '\\' and '"' in the string source by inserting a '\' before them.
Additionally all characters in the range 0x01-0x1F (everything below SPACE) and in the range 0x7F-0xFF (all non-ASCII chars) are replaced with a '\' followed by their octal representation. Characters supplied in exceptions are not escaped.