unicode: s/FEATURE_ASSUME_UNICODE/UNICODE_SUPPORT, add UNICODE_USING_LOCALE

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/libbb/Kbuild b/libbb/Kbuild
index 49cf4b8..4606d5a 100644
--- a/libbb/Kbuild
+++ b/libbb/Kbuild
@@ -124,7 +124,7 @@
 # and objects which may fail to build (SELinux on selinux-less system)
 lib-$(CONFIG_SELINUX) += selinux_common.o
 lib-$(CONFIG_FEATURE_MTAB_SUPPORT) += mtab.o
-lib-$(CONFIG_FEATURE_ASSUME_UNICODE) += unicode.o
+lib-$(CONFIG_UNICODE_SUPPORT) += unicode.o
 lib-$(CONFIG_FEATURE_CHECK_NAMES) += die_if_bad_username.o
 
 lib-$(CONFIG_LOSETUP) += loop.o