[release,automake] Fixes installation of files below am.

The am_DATA variable was set to EXTRA_DIST which contained
CMakeLists.txt. Therfore CMakeLists.txt was installed.
This patch fixes this by listing files to install in am_DATA
and using EXTRA_DIST only for those files that are otherwise
not distributed. Suprisingly, some files from am_DATA have to
be listed there, too.