Small revamp of medHUDs and secHUDs. Fixes del() lag (this time 5real).

SecHUDs and medHUDs (including pAIs and odyssesus) won't create a fucklod of images per tick and then disposal them, lagging like retards.

Now each human will have a list of the HUD images, that will be refreshed if it's required, lets say, a medic walking near you with a medHUD will refresh both of your medical hud images.
The list, called hud_list, uses seven(for now) defines for all the images, defined in the __DEFINES.dm

I also added a check for not rounding the health bar if the pacient it's dead, fixing some issues with showing dead people in critical or with possitive health.