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
So 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.