MFH: r548445

shells/zsh: Fix build with devel/ncurses 6.2

When devel/ncurses is installed in the system, the Zsh configure script
detects and uses ${LOCALBASE}/include/ncurses/ncurses.h instead.

The patch is obtained from this commit:
https://sourceforge.net/p/zsh/code/ci/c6a85163619ed1cee89ab047a0d98108ed46828d/

cc -c -I. -I../../Src -I../../Src -I../../Src/Zle -I. -I/usr/local/include -DBOOL_DEFINED -DLIBICONV_PLUG -DHAVE_CONFIG_H -DMODULE -O2 -pipe -DLIBICONV_PLUG -fstack-protector-strong -fno-strict-aliasing -fPIC -o curses..o curses.c
In file included from curses.c:210:
./curses_keys.h:93:15: error: use of undeclared identifier 'KEY_EVENT'

{"EVENT", KEY_EVENT},
          ^

1 error generated.

• Error code 1

Reviewed by: koobs
Approved by: koobs (ports, mentor)
Differential Revision: https://reviews.freebsd.org/D26355

Approved by: ports-secteam (fluffy)