Release 6.3 RELEASE_6_3

git-svn-id: https://svn.code.sf.net/p/smartmontools/code/trunk/smartmontools@3976 4ea69e1a-61f1-4043-bf83-b5c94c648137
Bump release number to 6.4

git-svn-id: https://svn.code.sf.net/p/smartmontools/code/trunk/smartmontools@3977 4ea69e1a-61f1-4043-bf83-b5c94c648137