Remove the size limitation on packed revprops per revision.
We don't enforce any such limits anywhere else.

* subversion/libsvn_fs_fs/fs_fs.c
  (parse_packed_revprops): bump limit from 16MB to "max addressable"

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1491770 13f79535-47bb-0310-9956-ffa450edef68