Unbreak the build with NLS unset

Autoreconf needs autopoint from gettext-tools, so we need gettext
all the time, not just when NLS is engaged.  But gettext-tools is
enough for non-NLS case, thus require it all the time and full
gettext will be pulled in only by builds with NLS enabled.

Index: mail/abook/Makefile
===================================================================
--- mail/abook/Makefile	(revision 429451)
+++ mail/abook/Makefile	(working copy)
@@ -11,7 +11,7 @@
 
 LICENSE=	GPLv2
 
-USES=		ncurses readline autoreconf localbase
+USES=		ncurses readline gettext-tools autoreconf localbase
 GNU_CONFIGURE=	yes
 
 PORTDOCS=	ANNOUNCE AUTHORS BUGS ChangeLog FAQ INSTALL NEWS README \