This is similar to the shell single-quote string. However, escapes
\ are honored before another escape, single quotes '
and hash characters #. This latter is done specifically
to disambiguate lines starting with a hash character inside
of a quoted string. In other words,
fumble = ' #endif ';
could be misinterpreted by the definitions scanner, whereas this would not:
fumble = ' \#endif ';
As with the double quote string, a series of these, even intermixed with double quote strings, will be concatenated together.