[PATCH] Do not disable txn-list-lock on Windows

Hi!

I've noticed that txn-list operations are not being synchronized on Windows
around trunk_at_1568806. FSFS makes use of two different types of locks: there
are mutexes synchronizing the fcntl file locking (POSIX only) and ordinary
mutexes (e.g. txn-list-lock). The former are only required on POSIX, the
latter, however, should be enabled under all OSes.

Since r1182459 [1], the txn-list-lock mutex is being erroneously enabled and
disabled under the same condition as the mutexes required for the fcntl locking
mechanism to work. This effectively makes the txn-list operations work without
any serialization on Windows.

I have attached a patch that fixes this problem. Log message:
[[[
Ensure that access to the 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.

Patch by: Evgeny Kotkov <evgeny.kotkov{_AT_}visualsvn.com>
]]]

[1] http://svn.apache.org/viewvc?view=revision&revision=r1182459

Thanks and regards,
Evgeny Kotkov