bug#1503: feature request: multiline header (and mode) lines

[Peter Mao]

I realize this requires tweaking of the C-code, but I'm not awesome
enough to do it myself:

Can emacs be given the gift of a header-line that word wraps, so that
the header can be more than one line tall?  I imagine the same could
go for the mode line, but I don't have a clear need for that right
now.  I know that the fringes can occupy > 1 column, so it seems like
an oversight if the header and mode lines are restricted to 1 line.

I've written a minor mode for reading/sorting physics abstracts from
the physics arXiv.  The mode either lists subdirectories directly
under the current directory, or recursively lists all subdirectories
of the pwd.  Either way, the list could potentially be longer than the
width of the screen, making some directory names unviewable.  A
multiline header would make it perfect.

I thought of putting that text in the buffer, but that makes it much
harder to update the text.

Peter Mao