Do "SCROLL to change player" visible in any standard aspect ratio

Above text was cut for aspect ratio 5:4 (quite much) and 4:3 (a little) for
previous value "left = (VIRTW*3/2)*6/8"
Two fixes concerning items selection in menu

The first fixes the last use of menusel, that wasn't checked for range yet.
The second one brings menusel back into range, if there is no
refresh function.
Show list of demos in "Download demo" menu
Prevent displaying remote servers on startup of LAN servers browser

After startup of LAN servers browser there appeared sometimes also remote
servers, instead of only LAN servers.
I such case "si.lastpingmillis=servermenumillis" for all remote servers.
So this commit changes a little existing condition, to prevent above
problem.
Drop activated grenade, when player switches to edit mode
Turn off sniper rifle's scope during intermission
Disable listdemos and getdemo in singleplayer
Removed unnecessary restrictions of switching to SPECTATOR team

Note: spectate() function doesn't have such restrictions.
Merge branch 'master' into next
Restore old working quicknadethrow code and fix bug in it

This commit restores old working quicknadethrow code, which existed after
commit: https://github.com/assaultcube/AC/commit/aaeca4ef323f09d252498bcc66eb90d51aef4586
and keeps later bug fixes (which thought needed to be fixed).
It fixes https://github.com/assaultcube/AC/issues/25

It also fixes followed bug: after releasing right mouse button/G key
and quickly pressing it again, weapon, to which quicknadethrow switched,
starts to shoot.