better wording in Config

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

Config.in

@@ -161,9 +161,11 @@ config LAST_SUPPORTED_WCHAR
 
 	  The idea is that many valid printable Unicode chars are
 	  nevertheless are not displayed correctly. Think about
-	  combining charachers, double-wide hieroglyphs and such.
-	  Many terminals, xterms and such will fail to handle them
-	  correctly.
+	  combining charachers, double-wide hieroglyphs, obscure
+	  characters in dozens of ancient scripts...
+	  Many terminals, terminal emulators, xterms etc will fail
+	  to handle them correctly. Choose the smallest value
+	  which suits your needs.
 
 	  Typical values are:
 	  126 - ASCII only
@@ -172,6 +174,10 @@ config LAST_SUPPORTED_WCHAR
 			code is ~700 bytes smaller for this case.
 	  4351 (0x10ff) - there are no double-wide chars in [0..4351] range,
 			code is ~300 bytes smaller for this case.
+	  12799 (0x31ff) - nearly all non-ideographic characters are
+			available in [0..12799] range, including
+			East Asian scripts like katakana, hiragana, hangul,
+			bopomofo...
 	  0 - off, any valid printable Unicode character will be printed.
 
 config UNICODE_COMBINING_WCHARS

libbb/unicode_wcwidth.c

@@ -534,6 +534,7 @@ static int wcwidth(unsigned ucs)
 		|| ucs == 0x2329 /* left-pointing angle bracket; also CJK punct. char */
 		|| ucs == 0x232a /* right-pointing angle bracket; also CJK punct. char */
 		|| (ucs >= 0x2e80 && ucs <= 0xa4cf && ucs != 0x303f) /* CJK ... Yi */
+#  if LAST_SUPPORTED_WCHAR >= 0xac00
 		|| (ucs >= 0xac00 && ucs <= 0xd7a3) /* Hangul Syllables */
 		|| (ucs >= 0xf900 && ucs <= 0xfaff) /* CJK Compatibility Ideographs */
 		|| (ucs >= 0xfe10 && ucs <= 0xfe19) /* Vertical forms */
@@ -541,6 +542,7 @@ static int wcwidth(unsigned ucs)
 		|| (ucs >= 0xff00 && ucs <= 0xff60) /* Fullwidth Forms */
 		|| (ucs >= 0xffe0 && ucs <= 0xffe6)
 		|| ((ucs >> 17) == (2 >> 1)) /* 20000..3ffff: Supplementary and Tertiary Ideographic Planes */
+#  endif
 		);
 # endif
 #endif