Fix socks5 handshake for username/password auth

The fix for bug 8117 exposed this bug, and it turns out real-world
applications like Pidgin do care. Bugfix on 0.2.3.2-alpha; fixes bug 8879.
Merge remote-tracking branch 'origin/maint-0.2.4'
Fix unit tests to pass after fix for #8879
Merge remote-tracking branch 'origin/maint-0.2.4'
Remove PK_PKCS1_PADDING

See #8792
Changes file for 8792