Release version 29

* NEWS: Record release date.
syntax-check: remove trailing whitespace.

* build-aux/sanity-cfg.mk (error-message-uppercase): Exclude
examples/socket.lua, which otherwise triggers false positives.
* NEWS, examples/socket.lua, examples/termios.lua, lposix.c:
Remove trailing whitespace.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>