When using older ffmpeg on the Mac the try_compiles are failing because a link error and thus were not producing accurate configuration results.

After talking with Brad King it is clear that the visibility support is
also useful for static linking.

Added the option to turn on stricter compiler flags (GCC only right
now), default to off. The flags are quite safe in VTK, but can cause
hundreds of warnings in some other projects code bases.

ENH: If compiling with OSMesa ON, make compiling with X optional.  It is not uncommon to use OSMesa in place of X11.

Sync the VTK copy of the FindPythonLibs module with CVS head. Main
change is a patch from Pat Marion to improve the Python modules macro.

ENH: Automatically setting the R_HOME environment variable to the value calculated by CMake at configuration time.  This will be overridden by the environment variable if present.  This may need further work for installed systems.

ENH: When using FFMPEG encoder, it first check if you are using a recent version of FFMPEG (or an old one as it was required previously for vtk). Then vtkFFMPEGWriter uses either the older API or the new one. See http://www.vtk.org/pipermail/vtk-developers/2009-December/006522.html. Original solution provided by Berk Geveci and improved by Nicolas Rannou.

After discussions with Brad King silencing the MSVC warning in this case. See
the comments in the source file, the symbols should be available at link time.

Turned off GCC visibility support by default. It seems that vtkImageIterator
and vtkArrayIteratorTemplate are declared in such a way that their symbols are
not exported correctly when using GCC visibility (they are members of other
classes), but removing the include seems to be causing issues with MSVC finding
the template implementation.

This flag causes GCC to fail with an error when a non-void function does not
return, but it is not present on all versions of GCC.

If VTK is being built standalone then support for GCC visibility is enabled
for the VTK kits. Additionally some GCC flags are added for Debug and
RelWithDebInfo builds to enable extra warnings and error when a non-void
function does not return anything.

ENH:  Added full paths to Matlab libraries for linking with external projects.