build system: introduce FEATURE_ASSUME_UNICODE

ls: use it. also do G trick. with UNICODE off:

function                                             old     new   delta
ls_main                                              843     871     +28
show_color                                             1       -      -1
showdirs                                             500     497      -3
my_stat                                              100      97      -3
terminal_width                                         4       -      -4
tabstops                                               4       -      -4
status                                               122     118      -4
static.dotdir                                          4       -      -4
current_time_t                                         4       -      -4
all_fmt                                                4       -      -4
------------------------------------------------------------------------------
(add/remove: 0/6 grow/shrink: 1/3 up/down: 28/-31)             Total: -3 bytes

Also was tested with UNICODE on with glibc.

1 files changed, 12 insertions, 0 deletions

diff --git a/Config.in b/Config.in
index 0a7edf84c..e70caf5a1 100644
--- a/Config.in
+++ b/Config.in
@@ -21,6 +21,18 @@ config DESKTOP
           Select this only if you plan to use busybox on full-blown
           desktop machine with common Linux distro, not on an embedded box.
 
+config FEATURE_ASSUME_UNICODE
+        bool "Assume that 1:1 char/glyph correspondence is not true"
+        default n
+        help
+          This makes various applets aware that one byte is not
+          one character on screen.
+
+          Busybox aims to eventually work correctly with Unicode displays.
+          Any older encodings are not guaranteed to work.
+          Probably by the time when busybox will be fully Unicode-clean,
+          other encodings will be mainly of historic interest.
+
 choice
         prompt "Buffer allocation policy"
         default FEATURE_BUFFERS_USE_MALLOC