Always treat NOTICEs received before registration as local server notices

We don't know the server's proper name until registration, so the test against
that isn't reliable.  We shouldn't be able to receive messages from anyone else
until we're registered, so this should be safe.

This requires changing serversay() to accept the from name instead of the
from_server.  While we're there, replace the use of alloca() with simpler
logic based on m_sprintf().

Changelog

@@ -1,5 +1,7 @@
 [Changes 1.2.2]
 
+* Treat all NOTICEs before registration as local server notices. (caf)
+
 * Add /on NOTICE_GROUP and /fset NOTICE_GROUP analogous to MSG_GROUP. (caf)
 
 * Add configure check for <sys/sockio.h>. (caf)