Issue #20546: Use specific asserts in int tests.
Issue #20555: Use specific asserts in urllib, httplib, ftplib, cgi, wsgiref tests.
Issue #20549: Use specific asserts in mailbox, smtplib and poplib tests.
Issue #20406: Use Python application icons for Idle window title bars.
Patch mostly by Serhiy Storchaka.
#14983: always add a line end after a MIME boundary marker.

This is more RFC compliant (see issue) and fixes a problem with
signature verifiers rejecting the part when signed.  There is some
amount of backward compatibility concern here since it changes
the output, but the RFC issue coupled with fixing the problem
with signature verifiers seems worth the small risk of breaking
code that depends on the current incorrect output.