attempt to make unit tests more likely to clean up proxy processes after themselves

git-svn-id: https://svn.code.sf.net/p/libtorrent/code/trunk@8741 a83610d8-ad2a-0410-a6ab-fc0612d85776
extend peer_plugin to also be notified of disconnects and successful connect events

git-svn-id: https://svn.code.sf.net/p/libtorrent/code/trunk@8742 a83610d8-ad2a-0410-a6ab-fc0612d85776
optimize test_transfer to fail faster

git-svn-id: https://svn.code.sf.net/p/libtorrent/code/trunk@8743 a83610d8-ad2a-0410-a6ab-fc0612d85776
be more forgiving of slow (or busy) hardware in test_transfer

git-svn-id: https://svn.code.sf.net/p/libtorrent/code/trunk@8744 a83610d8-ad2a-0410-a6ab-fc0612d85776
raise time limit for unit tests. improve logging of udp tracker test

git-svn-id: https://svn.code.sf.net/p/libtorrent/code/trunk@8745 a83610d8-ad2a-0410-a6ab-fc0612d85776