Merge pull request #14 from cvmfs/master

pull from upstream cvmfs
Moved include of inttypes.h from sync_union.cc to sync_union.h (caused compile
error on my machine since uint64_t was no longer defined in sync_union.h (used
to be included via platform.h)
Merge pull request #207 from wtsi-hgi/hotfix-overlayfs-compile

fixed compile failure due to inttypes.h not being included in sync_union.h