adding support for triply-quoted strings, and de-supporting strings with embedded newlines.  also adding support for unterminated strings (which now can go at most to the nearest end of the line), both in parsing and in CSS display.  adding a dummy production of "bad-expr" so that the parser can always shift the bad token before getting stuck, which helps ensure a consistent reporting of error location.
new bootstrap with support for new string literals.  will produce a new bootstrap again after reverting the changes to the compiler's docstrings (which needed to not use multiline literals or triple-quoted literals in order to build the bootstrap...)
new bootstrap
restoring multiline string literals in the compiler, now that the bootstrap can support it