Add support for a third color in face definition that controls
the underline and a 'c' attribute for curly underline (that takes
precedence over 'u' if both are specified)
Allow empty colors to mean default, so that `,,red+u` means the
same as `default,default,red+u`
Fixes#4138
First try to break at a whitespace, if that fails (likely because
that last WORD is too long for the wrapping width), then try to
wrap at a 'word' boundary (on a non alphanumeric character).
Fixes#3048