clean feeds at maint time

[oxarbitrage]

the pull attempts to remove not needed feeds from the bitasset object at maint time. it deletes the feeds that are expired according to the options (default 1 day) and it keep the min number of feeds required(default 7).

problem is replay fails at here:

2883742ms th_a       application.cpp:499           handle_block         ] Got block: #60000 time: 2015-10-15T18:13:18 latency: 71948085742 ms from: triox-delegate  irreversible: 59979 (-21)
2885695ms th_a       db_block.cpp:202              _push_block          ] Failed to push new block:
10 assert_exception: Assert Exception
d.get_balance(*_paying_account, _bitasset_data->options.short_backing_asset(d)) >= o.delta_collateral: Cannot increase collateral by 433763148 when payer only has 28651500
    {"c":433763148,"b":28651500}
    th_a  market_evaluator.cpp:161 do_evaluate

    {"o":{"fee":{"amount":2000000,"asset_id":"1.3.0"},"funding_account":"1.2.91204","delta_collateral":{"amount":433763148,"asset_id":"1.3.0"},"delta_debt":{"amount":0,"asset_id":"1.3.121"},"extensions":[]}}
    th_a  market_evaluator.cpp:165 do_evaluate

    {}
    th_a  evaluator.cpp:51 start_evaluate

    {"op":[3,{"fee":{"amount":2000000,"asset_id":"1.3.0"},"funding_account":"1.2.91204","delta_collateral":{"amount":433763148,"asset_id":"1.3.0"},"delta_debt":{"amount":0,"asset_id":"1.3.121"},"extensions":[]}]}
    th_a  db_block.cpp:645 apply_operation

    {"trx":{"ref_block_num":64327,"ref_block_prefix":2666126845,"expiration":"2015-10-15T21:52:45","operations":[[3,{"fee":{"amount":2000000,"asset_id":"1.3.0"},"funding_account":"1.2.91204","delta_collateral":{"amount":433763148,"asset_id":"1.3.0"},"delta_debt":{"amount":0,"asset_id":"1.3.121"},"extensions":[]}]],"extensions":[],"signatures":["207e751b2029bc07a71dc83a581d9a80c196244d2a13aca71131c11e49783886853eb9a846fb82d674ab7636b330d0e33a8041c3f26f957e8c98e95ad8e6921ae0"]}}
    th_a  db_block.cpp:628 _apply_transaction

    {"next_block.block_num()":64329}
    th_a  db_block.cpp:545 _apply_block
2885695ms th_a       application.cpp:531           handle_block         ] Error when pushing block:
10 assert_exception: Assert Exception
d.get_balance(*_paying_account, _bitasset_data->options.short_backing_asset(d)) >= o.delta_collateral: Cannot increase collateral by 433763148 when payer only has 28651500

any light in this is appreciated, i cant get why it is failing.

[abitmore]

There was a bug about feed expiration, which was fixed with a hard fork, perhaps related.

      if( head_block_time() < HARDFORK_615_TIME )
         feed_is_expired = b.feed_is_expired_before_hardfork_615( head_block_time() );
      else
         feed_is_expired = b.feed_is_expired( head_block_time() );

[oxarbitrage]

replaced by #832