Bump version numbers for 0.8 release

Version numbers changed from 0.7.99 to 0.8.0
Set CLIENT_VERSION_IS_RELEASE to remove pre-release warning
Updated copyright in COPYING and doc/READMEs to 2013
Updated doc/release-notes.txt
Merge commit 'd38c6488d067c2e88726e2ca99bc76fd67dab49b'