Always release field logs when we drop them.
Adjust how first and after modes work to make them easier to test.
Change stream checking code, fix leaks and double frees.
Add mustStash(), mustSwap(), streamReset(), drop mustPassOld().
Modify test code to check free-list count and release all of
the field-logs returned by the filter; it must release any of
the field-logs that it decides to drop.
Andrew Johnson
8ff6ce4821