[8378] Use exceptions instead of explicit size checking for each packet

CHECK_PACKET_SIZE was pretty error prone; once it was forgotten mangosd
could crash due to the asserts in ByteBuffer.h. That was exploitable by
malicious players.
Furthermore, there were duplicate checks: Additionally to
CHECK_PACKET_SIZE, the ByteBuffer assertions keept an eye
on not exceeding the packet boundaries - just to crash the server for
sure in such a case.
To prevent memory leaks or other undesirable states, please read in
every handler all variables _before_ doing any concrete handling.

src/realmd/AuthSocket.cpp

@@ -766,6 +766,7 @@ bool AuthSocket::_HandleReconnectChallenge()
 
     _login = (const char*)ch->I;
     _safelogin = _login;
+    loginDatabase.escape_string(_safelogin);
 
     QueryResult *result = loginDatabase.PQuery ("SELECT sessionkey FROM account WHERE username = '%s'", _safelogin.c_str ());