Fixed spelling: DECOMPOZITION --> DECOMPOSITION.

Also added the DEBUG flag to CFLAGS in the makefile.
Cleaned up debug printf macro. Removed the misleading loop syntax, also the
conditional preprocessing now requires NDEBUG to be defined in order to
*disable* debug printf's; printing is enabled by default. NDEBUG is a good
feature test macro to use since it also controls compilation of assert().
simulation.c: dprintf --> debug_printf
New filed utils.h and .c. They currently just provide a checked_malloc
function.

Updated the makefile to include utils.c in the source list.
newWorld initialises the grid as a two dimensional matrix. Changed the
definition of struct world to reflect the new type for map (Tile * -->
Tile **).

Also removed a few function definitions from world.h, since the functions
are only being called from inside world.c.
Changed the GET_TILE macro so that world.o builds. This is a horrible
kludge, and is totally unsafe since there is no array bounds checking, but
rest assured that I will be replacing this macro soon.
Merge remote-tracking branch 'origin/matt'

Conflicts:
	Makefile
	constants.h
	simulation.c
	world.c
	world.h
Documentation of structures and functions, ...

fixed finishStep
removed tiredness and lastSlept attributes of LivingEntities