bug#37564: [PATCH] don't export LINES and COLUMNS env vars in term to fix ncurses applications

[Glenn Morris]

PS for an example of the effect, one can use some of the programs in
the ncurses-examples from
https://invisible-island.net/ncurses/ncurses-examples.html

eg "worm".

If I run it in an xfce4-terminal, then maximise the terminal, the worms
spread over the whole screen.
If I "export LINES" and COLUMNS beforehand, then the worms don't expand
beyond the original terminal size.

The same effect is visible in Emacs's M-x term with and without the
LINES/COLUMNS variables.