Changes to fire sound functions and files

[paramat]

Due to the original code being very intensive, buggy and containing errors, the fire sound code has been rewritten.

We have made an effort to not break mods:

Mods that call the function 'fire.update_sounds_around(pos)' will not cause errors but nothing will happen because we have kept that function as an empty function.
During this next release cycle you should update your mods to no longer call this function as it will be removed at 0.4.16.

The fire sound files 'fire_small.ogg' and 'fire_large.ogg' are no longer used by the mod but have been left in temporarily to not break mods that may be using them. During the next release cycle you should copy these files into your own mods, they will be removed at 0.4.16.