Fixes an instakill exploit with extinguishers.

fixes #169 (closed)

I've tried different solutions to this, such as changing the following

thing.throw_at(target,10,rand(12,14))

to the following

thing.throw_at(target,10,thing.throw_speed*2)

but this results in it doubling thing's throw_speed on thing itself rather than just a once off thing when fired.

Same thing happens with the following:

var/newspeed = thing.throw_speed*2
thing.throw_at(target,10,newspeed)

Magic numbers should fix as a temporary solution for now.