Increment CP2K development version number

git-svn-id: svn://svn.code.sf.net/p/cp2k/code/trunk@12977 bac0169d-1eea-4375-b5f6-f89d2ced9994

Increment version number of the current development version to 2.4 af…

…ter the release of the CP2K version 2.3

git-svn-id: svn://svn.code.sf.net/p/cp2k/code/trunk@12358 bac0169d-1eea-4375-b5f6-f89d2ced9994