#24 newlines in cells should be escaped

[Anonymous]

When a table cell contains a newline character (say its contents are
"hello\nworld") that character is not escaped in the various output
formats. In TXT it makes it harder to parse and ambiguous; in HTML it is
wrong.

We get respectively:

(1, 1) = Hello
world
(1, 2) = ...

and:

<td>Hello
world</td>

(even though blanks are not significant in HTML.)