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 0a7edf8..e70caf5 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