Rename our struct statvfs to struct ustatvfs to prevent libc name collision.
Rename our struct statvfs to struct ustatvfs to prevent libc name collision.

jrk/unionfs-fuse,jrk/unionfs-fuse,yogoloth/unionfs-fuse,evnu/unionfs-fuse,yogoloth/unionfs-fuse,kissthink/unionfs-fuse-1,evnu/unionfs-fuse,jrk/unionfs-fuse,yogoloth/unionfs-fuse,kissthink/unionfs-fuse-1,kissthink/unionfs-fuse-1,jrk/unionfs-fuse,evnu/unionfs-fuse