This adds copyright/license notification blocks CMake's find-modules.
Many of the modules had no notices at all. Some had notices referring
to the BSD license already. This commit normalizes existing notices and
adds missing notices.
- Defines FIND_PACKAGE_MESSAGE function to help display
find result messages only once
- Added use of it to FindPackageHandleStandardArgs
- Added use of it to FindQt4, and FindX11
- This cleans up repeated messages in big projects