curses: Remove OpenBSD workaround

I removed the same sort of workaround for OpenBSD within the
configure script with commit 4dcc3f58
but didn't bother to grep further to come across this same chunk
of code in the curses code itself. So the following diff removes
the same workaround chunk within the curses code.

Signed-off-by: Brad Smith <brad@comstyle.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>