[Cmake] SOURCE_FILES deprecation

[Amitha Perera]

Hi all

I recently updated to latest CVS CMake and found that SOURCE_FILES is
marked as "deprecated" in version 1.4, but acts as if it were
removed. I suggest that it stay deprecated in the sense that it will
work, but will issue warnings. This will make the transition from 1.2
to 1.4 easier.

In particular, we have an informal agreement that vxl will compile
with the latest released CMake. I don't want people to *have* to
update to the latest CMake immediately--hopefully people can upgrade
as they get tired of the warnings.

It also makes it possible for me to test that certain parts of 1.4
work for vxl without having to switch the whole thing to 1.4.

Perhaps deprecation of commands can be done over two stages where
possible? 1.n+2 marks some commands in 1.n as deprecated; 1.n+4
removes those commands.

Thanks,
Amitha.