[CMake] portable cp and mv commands

[Brandon J. Van Every]

Does CMake 2.4 have 'em?  I'm writing some custom commands, and the 
utility I'm working with is too braindead to have its own file input and 
output flags.  So I'm hacking around it with cp and mv.  This is going 
to fail on systems that don't have cp and mv.  I could repurpose 
CONFIGURE_FILE but that seems hackerish.  I didn't see any modules for 
portable file operations.  FILE() appears to be missing a COPY command, 
although it does have a REMOVE.

Cheers,
Brandon Van Every