To do that, split up the Accounts objects and the instruction
implementations.
GPL code is only used when the "enable-gpl" feature is enabled. That
means compiling the program or running tests need explicit feature
activation now.
- Rename to perp_liq_base_or_positive_pnl and perp_liq_negative_pnl_or_bankruptcy
- Deal with situations where overall asset weight is zero and base position reduction
would not improve liqee health
- Add ability for liqors to take over positive unsettled pnl if that improves liqee health