Fix T53707: Error on export FBX object [PointLighs].

Inverse Coefficients decay method was added later, never made it to FBX
exporter.

Note that this is very limited approxiamtion/simplification here, we
cannot really export this correctly.

To be backported to 2.79a.

io_scene_fbx/__init__.py

@@ -21,7 +21,7 @@
 bl_info = {
     "name": "FBX format",
     "author": "Campbell Barton, Bastien Montagne, Jens Restemeier",
-    "version": (3, 8, 4),
+    "version": (3, 8, 5),
     "blender": (2, 79, 1),
     "location": "File > Import-Export",
     "description": "FBX IO meshes, UV's, vertex colors, materials, textures, cameras, lamps and actions",

io_scene_fbx/fbx_utils.py

@@ -94,6 +94,7 @@ FBX_LIGHT_DECAY_TYPES = {
     'CONSTANT': 0,                   # None.
     'INVERSE_LINEAR': 1,             # Linear.
     'INVERSE_SQUARE': 2,             # Quadratic.
+    'INVERSE_COEFFICIENTS': 2,       # Quadratic...
     'CUSTOM_CURVE': 2,               # Quadratic.
     'LINEAR_QUADRATIC_WEIGHTED': 2,  # Quadratic.
 }