[CMake] CMAKE_POSITION_INDEPENDENT_CODE Version

[Rob McDonald]

CMAKE_POSITION_INDEPENDENT_CODE first appears in the documentation for
2.8.9 while CMAKE_POSITION_INDEPENDENT_FLAGS appears in the docs for
2.8.8 -- with the same description.

Was this just a documentation typo, or did the name of this variable
change from 2.8.8 to 2.8.9?  Only the _FLAGS version is tracked in the
compatibility matrix on the Wiki...

https://cmake.org/Wiki/CMake_Version_Compatibility_Matrix

Which should I use to work with the widest range of CMake versions?

Rob