Intermediate commit to show a bug

Reference of the bug why this commit exists :
issue #451 from christopho/solarus

When open the console and type "hero:start_frozen(2000)" (or any number)
the game crashes after 2s, depending of what you left as error in the
code. The files to modify are data/physical_condition.lua and
data/entities/frozen_state.lua
Bugged version

To make it bug : go to lost palazzo, take the teleporter, use F4, take the
damage and... Wait...
Added sounds to sort and fix a small bug

Sounds are for the frozen state. Small bug about the sprite declaration
(num_frames was not corresponding with the no delay for "frozen"
animation)
Enhancement of frozen state

There is sound, it only miss a little modification on the freezing sound
(a little too long to be launched) and the sprite for the shattering and
all will be ok with it.
Cut of the sound for frozen state freezing
Sprite of frozen state Shattering OK

Frozen State seems to be ok now.
Merge branch 'develop'