Fix some bugs introduced in my prev. commits:

- Game::reconstructEntityGrid() now really clears only entity grid,
and not the tile grid as well
(Added OT_INVISIBLEENT do further distinguish entity from tile obstruction)

- Invalid script pointers should not pop up message boxes

- Lost an include and CMakeLists changes

CMakeLists.txt

@@ -363,6 +363,7 @@ SET(BBGE_SRCS
     ${BBGEDIR}/DarkLayer.cpp
     ${BBGEDIR}/Datafile.cpp
     ${BBGEDIR}/DebugFont.cpp
+    ${BBGEDIR}/DeflateCompressor.cpp
     ${BBGEDIR}/DFSprite.cpp
     ${BBGEDIR}/Effects.cpp
     ${BBGEDIR}/Emitter.cpp