Create dmtcp_checkpoint symlink during build time.

git-svn-id: svn://svn.code.sf.net/p/dmtcp/code/trunk@2421 ba6dc0ae-232f-0410-883f-9ebac64fc565
Updated restore logic for CWD on restart.

git-svn-id: svn://svn.code.sf.net/p/dmtcp/code/trunk@2422 ba6dc0ae-232f-0410-883f-9ebac64fc565
Docs for restoring CWD and multi-arch support.

git-svn-id: svn://svn.code.sf.net/p/dmtcp/code/trunk@2423 ba6dc0ae-232f-0410-883f-9ebac64fc565