This behavior makes includes in modules shipped with CMake still look
in the module directories defined by the project.  The change does not
effect building IceT on its own.  (At least, there are currently no
modules included that are also included with CMake.)  However, this is
currently necessary to prevent warnings in ParaView.

Support latest means of loading packages.  Add check for version.
Export targets correctly.

This completes the changes in the documentation.

- icetUnsafeStateGet now returns const.
- new ICET_COLLECT_TIME timing metric.
- ICET_COLLECT_IMAGES option.
- ICET_VALID_PIXELS_* state variables.
- Matrix helper functions.
- Input array for icetSendRecvLargeMessages became const.
- Background correction in strategies.

The latest MSVC debugger apparently checks to make sure that any
variable used as an argument to a function has been set.  There was
an instance in the reduce strategy that violated it.  I don't think
it could ever cause a problem (the arguments are ignored in this
particular state), but it's still bad programming style.  Thanks
to John Biddiscombe for bringing this up.

- ICET_MAGIC_K and ICET_MAX_IMAGE_SPLIT CMake, env, & IceT variables.
- icetCompressedCompressedComposite.
- Sparse image copy and split.
- Image interlacing.
- Image equal functions.
- icetDecompressSubImage.
- icetRenderTransferSparseImages.
- Sparse image null functions.

Now accepts and returns sparse images.  Also no longer collects image
pieces.

- Radix-k and its selection.
- icetAddTiles raises ICET_INVALID_VALUE for 0-pixel tile.
- icetFindRankInGroup and icetFindMyRankInGroup.
- New communication functions.
- Sequential strategy skips some collective operations.
- icetImageAssignBuffer and icetSparseImageAssignBuffer.
- ICET_SIZE_TYPE.
- ICET_IN_PLACE_COLLECT.

All the interesting changes on Release were already in master.  This
merge is basically for safety sake.

Use it to correct some background correction problems with blank tiles.

Makes us more assured that a failure will actually be reported as such.

Previously background correct only happened on display processes after
the image was collected.  Now we encourage distributed correction before
collection.  In this case, it was wrong to not correct on non-display
processes.

This also enables background correction in the sequential and reduce
strategies.

Created new state variables to capture the final background and a
flag whether the correction is really necessary.  Also moved the
background correct function to image.c, but it is not used yet.