cl_parse.c: hack so demos playback at the correct speed even if they contain a lot of svc_stufftext messages (e.g. one every frame).

for a test case, play a demo from: http://www.quaketastic.com/upload/files/demos/otp_honey100.zip
for the honey map pack: http://www.quaketastic.com/upload/files/single_player/maps/honey.zip
on a slow pc that gets signifigantly less than 72fps, or with host_maxfps lowered (e.g. set to 33).

with QS 0.85.9, the demo will play in slow-motion; with QS 0.85.6 (without the cross-map demo support) it plays normally.

admittedly this is a fringe scenario, but it's imo a legitimate bug in the Pa3PyX cross-map demo playback code.

git-svn-id: svn://svn.code.sf.net/p/quakespasm/code/trunk/quakespasm@974 af15c1b1-3010-417e-b628-4374ebc0bcbd