Use svn_cstring_strtoui64 in place of strtoul and ULONG_MAX.  Also
don't serialise negative lengths as part of a hash since we are, and
always been, deserialising as unsigned.

* subversion/libsvn_fs_base/lock.c
  (svn_fs_base__get_locks): Use svn_cstring_strtoui64.

* subversion/libsvn_subr/hash.c
  (hash_read): svn_cstring_strtoui64.
  (hash_write): Don't write negative lengths.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1460628 13f79535-47bb-0310-9956-ffa450edef68