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:
c6a8516361/

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
MFH:		2020Q3 (build fix)

shells/zsh/Makefile

@@ -88,6 +88,10 @@ SUB_FILES=	pkg-message
 CONFIGURE_ENV+=	ac_cv_lib_iconv_libiconv=no
 .endif
 
+.if ${ncurses_ARGS} == port
+EXTRA_PATCHES=	${PATCHDIR}/extra-patch-Src_Modules_curses__keys.awk
+.endif
+
 post-patch:
 # FreeBSD's clock_gettime(2) is in libc, not librt; see PR 167857
 	@${REINPLACE_CMD} -e '/LIBS/s|-lrt||' ${WRKSRC}/configure

shells/zsh/files/extra-patch-Src_Modules_curses__keys.awk

@@ -0,0 +1,18 @@
+https://sourceforge.net/p/zsh/code/ci/c6a85163619ed1cee89ab047a0d98108ed46828d/
+--- Src/Modules/curses_keys.awk.orig	2017-12-04 14:09:36 UTC
++++ Src/Modules/curses_keys.awk
+@@ -12,8 +12,13 @@ BEGIN {nkeydefs = 0}
+ 
+ END {
+     printf("static const struct zcurses_namenumberpair keypad_names[] = {\n")
+-    for (i = 0; i < 0 + nkeydefs; i++)
++    for (i = 0; i < 0 + nkeydefs; i++) {
++        if (name[i] == "EVENT")
++            printf("#ifdef KEY_EVENT\n")
+         printf("    {\"%s\", KEY_%s},\n", name[i], name[i])
++        if (name[i] == "EVENT")
++            printf("#endif\n")
++    }
+     printf("    {NULL, 0}\n")
+     printf("};\n")
+ }