Only match nicks and channels when told to, and not when not told to.

Previously things like /who account a%.. would be matched against a nick too
and /who realname r% would be matched against nicks and channels
(eg. when searching for users with a realname that's also a valid channel name,
or happens to be also a nick that is in use).

diff -r ebda89dbc5c9 ircd/m_who.c
--- a/ircd/m_who.c	Thu Jan 22 16:05:40 2009 +0100
+++ b/ircd/m_who.c	Thu Jan 22 16:29:28 2009 +0100
@@ -300,8 +300,11 @@
   who_marker = get_client_marker();
   commas = (mask && strchr(mask, ','));
 
-  /* First treat mask as a list of plain nicks/channels */
-  if (mask)
+  /* First treat mask as a list of plain nicks/channels
+   *  but only when told to match nicks (and channels)
+   *   with WHO_FIELD_NIC or when we got a mask with commas
+   */
+  if (mask && (matchsel & WHO_FIELD_NIC || commas))
   {
     strcpy(mymask, mask);
     for (p = 0, nick = ircd_strtok(&p, mymask, ","); nick;