[MP] Restrict sv_privateClients to 0...MAX_CLIENTS.
I will leave setting it to an otherwise correct value up to the server's judgement.
[MP] Merged critical fixes (ioquake/ioq3@f725b23) for snapshot floating point imprecision from ioq3 that were missing.

Also merged: part of ioquake/ioq3@e41d081
* Loopback clients only get snapshots at the server frame rate now
  (Anonymous <nkylqinhvgcbyl@mailinator.com>)
* cl_lanForcePackets. When set to 0 (default is 1) the cl_maxpackets setting
  will be ignored if on a LAN. (Anonymous <nkylqinhvgcbyl@mailinator.com>)
[MP] Attempt fixing snaps clamping to sv_fps/sv_snapsMin/sv_snapsMax changes at runtime correctly.
[MP] Merged fix from ioq3 that was reported by me: ioquake/ioq3@983ebbb
Ignore -psn* arguments on Mac OS X
Mac OS X adds an argument starting with "-psn" when launched using Finder, Dock,
or a terminal using open command and not specifying arguments.

It caused the opening videos to be skipped.

This change mimics SDL 1.2.
[MP] Remove a plus that shouldn't be there.
[MP] Use #ifdef not #if from previous commit.