remove outdated twisted test
WSA4000: stream_start, stream_stop, stream_status
:sweep:flush no longer exists
WSA4000: add system_flush, system_abort
Revert ":sweep:flush no longer exists"

This reverts commit 9657756f253b71286085b664df06928bf496e6f3.
:sweep:flush is dead; long live :system:flush
rename system_abort to abort, more like other methods
WSA4000: improve spp()
stream speed test example