Pass ncurses cflags to build

Fixes #25
Note from William Hubbs:
The original patch overwrote CFLAGS. I modified this patch to add the
ncurses cflags to CPPFLAGS instead of overwriting CFLAGS.

mk/termcap.mk

@@ -1,11 +1,12 @@
 ifeq (${MKTERMCAP},ncurses)
+TERMCAP_CFLAGS:=	$(shell pkg-config ncurses --cflags 2> /dev/null)
 LTERMCAP:=			$(shell pkg-config ncurses --libs 2> /dev/null)
 ifeq ($(LTERMCAP),)
 LIBTERMCAP?=	-lncurses
 else
 LIBTERMCAP?= $(LTERMCAP)
 endif
-CPPFLAGS+=	-DHAVE_TERMCAP
+CPPFLAGS+=	-DHAVE_TERMCAP ${TERMCAP_CFLAGS}
 LDADD+=		${LIBTERMCAP}
 else ifeq (${MKTERMCAP},termcap)
 LIBTERMCAP?=	-ltermcap