bsddialog: import new TUI widget and utility

bsddialog is an attempt to write in permissive license a replacement for
libdialog.

While it is still in early stage it is good enough to already be used in
many areas, it is imported as private lib until it matures enough to be
considered as having a stable ABI

etc/mtree/BSD.usr.dist

@@ -9,6 +9,8 @@
     ..
     include
         private
+            bsddialog
+            ..
             bsdstat
             ..
             event1

lib/Makefile

@@ -36,6 +36,7 @@ SUBDIR=	${SUBDIR_BOOTSTRAP} \
 	libauditd \
 	libbegemot \
 	libblocksruntime \
+	libbsddialog \
 	libbsdstat \
 	libbsm \
 	libbz2 \

share/mk/src.libnames.mk

@@ -16,6 +16,7 @@ _PRIVATELIBS=	\
 		atf_c \
 		atf_cxx \
 		auditd \
+		bsddialog \
 		bsdstat \
 		cbor \
 		devdctl \
@@ -262,6 +263,7 @@ _DP_80211=	sbuf bsdxml
 _DP_9p=		sbuf
 _DP_archive=	z bz2 lzma bsdxml zstd
 _DP_avl=	spl
+_DP_bsddialog=	formw ncursesw tinfow
 _DP_zstd=	pthread
 .if ${MK_BLACKLIST} != "no"
 _DP_blacklist+=	pthread