[cmake-developers] Add command line options for deprecation message control

[Domen Vrankar]

> The branch seems to make the RunCMake.CPack_RPM test fail on my machine. I
> have not investigated.

Missed this thread... I was talking to Brad about this.
Failing test is written exactly for testing author warning message
(CPackRPM.cmake:560). RPM packages may be relocatable but if
relocation paths don't match with any file paths in package an author
warning is output but package is still created.

Since CPack only gets CPACK_* variables from CMake we can't use
CMAKE_SUPPRESS_DEVELOPER_ERRORS to revert back to warnings. If this is
the only location where CPack uses developer messages we could change
it to normal info message but implementing this fallback mechanism for
CPack (and CTest?) would probably be a more complete solution.

Regards,
Domen