tweaking Unicode support

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/include/unicode.h b/include/unicode.h
index be64a50..e006147 100644
--- a/include/unicode.h
+++ b/include/unicode.h
@@ -7,10 +7,13 @@
 
 #if !ENABLE_FEATURE_ASSUME_UNICODE
 
+# define bb_mbstrlen(string) strlen(string)
 # define check_unicode_in_env() ((void)0)
 
 #else
 
+size_t bb_mbstrlen(const char *string) FAST_FUNC;
+
 # if ENABLE_LOCALE_SUPPORT
 
 #  include <wchar.h>
@@ -19,6 +22,8 @@
 
 # else
 
+/* Crude "locale support" which knows only C and Unicode locales */
+
 #  if !ENABLE_FEATURE_CHECK_UNICODE_IN_ENV
 #   define check_unicode_in_env() ((void)0)
 #  else
@@ -50,8 +55,8 @@
 int iswalnum(wint_t wc) FAST_FUNC;
 int iswpunct(wint_t wc) FAST_FUNC;
 
-# endif
+# endif /* !LOCALE_SUPPORT */
 
-#endif
+#endif /* FEATURE_ASSUME_UNICODE */
 
 #endif