Permit 0xa0, if it appears inside UTF8 (via set::allowed-nickchars).

This is the "non breaking space" outside UTF8 and thus was previously
blacklisted. Keeping it blacklisted even if it appears in UTF8 is not
really an option as it means some UTF8 characters can never be used,
like the letter "nun" in Hebrew, and likely others.

src/modules/charsys.c

@@ -152,7 +152,6 @@ ILangList *ilanglist = NULL;
 /* These characters are ALWAYS disallowed... from remote, in
  * multibyte, etc.. even though this might mean a certain
  * (legit) character cannot be used (eg: in chinese GBK).
- * - no breaking space
  * - ! (nick!user seperator)
  * - prefix chars: +, %, @, &, ~
  * - channel chars: #
@@ -161,7 +160,7 @@ ILangList *ilanglist = NULL;
  * [CHANGING THIS WILL CAUSE SECURITY/SYNCH PROBLEMS AND WILL
  *  VIOLATE YOUR ""RIGHT"" ON SUPPORT IMMEDIATELY]
  */
-const char *illegalnickchars = "\xA0!+%@&~#$:'\"?*,.";
+const char *illegalnickchars = "!+%@&~#$:'\"?*,.";
 
 /* Forward declarations */
 int _do_nick_name(char *nick);