Fix for issue3870 "File descriptor leaks during svnsync". Before this fix, all of destination delta editor's interfaces are called with *LONG* living pool(dst_rev_pool living for one full revision). This makes it a memory bloat and bloat of other OS resources like file descriptors to live as long the dst_rev_pool. * subversion/libsvn_ra_serf/replay.c (replay_context_t.file_pool): New pool of file scope. (start_replay): clear the file_pool. Use file_pool for dest editor's file operations. (end_replay): Use file_pool for dest editor's file operations. (svn_ra_serf__replay, svn_ra_serf__replay_range): Create a new pool 'replay_ctx->file_pool'. * subversion/tests/cmdline/svnsync_tests.py (fd_leak_sync_from_serf_to_local): Remove XFail marker. Patch by: kameshj Arwin Arni