Change the working copy exclusive locking default to off and require
explict enabling by the user.  Allow Windows users to enable exclusive
locking.

* subversion/include/svn_config.h
  (SVN_CONFIG_OPTION_SQLITE_EXCLUSIVE_CLIENTS): New.

* subversion/libsvn_subr/config_file.c
  (svn_config_ensure): Add new option to default file contents.

* subversion/svn/svn.c
  (SVN_CL_NO_DEFAULT_EXCLUSIVE_LOCK): Rename to ...
  (SVN_CL_NO_EXCLUSIVE_LOCK): ... this.
  (sub_main): Use new option.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1447716 13f79535-47bb-0310-9956-ffa450edef68