This is r61508 plus additional fixes to the handling of 'limit'

in TextIOWrapper.readline().

All tests now pass for me (except for expected skips on darwin:
bsddb, bsddb3, cProfile, codecmaps_*, curses, gdbm, largefile,
locale, normalization, ossaudiodev, pep277, socketserver,
startfile, timeout, urllib2net, urllibnet, winreg, winsound,
xmlrpc_net, zipfile64, and the -u largefile part of test_io).