message: Add a DEPRECATION mode

By default, the message is not issued. If CMAKE_ERROR_DEPRECATED
is on, the message is fatal. If CMAKE_WARN_DEPRECATED is on, the
message is a warning.
Qt4Macros: Port to use message(DEPRECATION)
Merge topic 'deprecation-message' into next

ce62aa2 Qt4Macros: Port to use message(DEPRECATION)
509c142 message: Add a DEPRECATION mode