Ensure that access to the fsfs transaction list and free transaction
pointer is properly synchronized on Windows.  Before this changeset,
the corresponding txn-list-lock mutex was being enabled/disabled under
the same condition as the mutexes required for the POSIX fcntl file
locking.  This effectively ended up in no synchronization for the
txn-list operations on Windows.

* subversion/libsvn_fs_fs/fs.c
  (fs_serialized_init): Unconditionally enable the TXN_LIST_LOCK mutex
    when using a threaded APR.

Patch by: Evgeny Kotkov <evgeny.kotkov{_AT_}visualsvn.com>
          (tweaked by me)

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1568953 13f79535-47bb-0310-9956-ffa450edef68