Bugfix (introduced: 20090614): with concurrent connections
from the same client IP address, and after-220 tests enabled,
postscreen could overwrite the cached "all tests completed"
result of one connection that completed the after-220 tests,
with the "some tests not completed" result of a concurrent
connection where the client hung up before completing the
after-220 tests.  Files: postscreen_misc.c, postscreen_state.c,
postscreen.h, postscreen_tests.c, postscreen.c, postscreen_smtpd.c,
postscreen_early.c.

Cleanup: don't try to optimize away postscreen cache updates.
File: postscreen_misc.c.

Cleanup: removed compatibility crutches that emulated a
historical data organization from four years ago. Files:
postscreen/postscreen.[hc], postscreen/postscreen_early.c,
postscreen/postscreen_smtpd.c, postscreen/postscreen_tests.c.