xfsprogs: do not redeclare globals provided by libraries

xfsprogs: do not redeclare globals provided by libraries

In each of these cases, db, logprint, and mdrestore are redeclaring
as a global variable something which was already provided by a
library they link with.

gcc now defaults to -fno-common and trips over these global variables
which are declared in utilities as well as in libxfs and libxlog, and
it causes the build to fail.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>