add __interact_read_ucs and __interact_written_ucs

unicode-safe versions of __interact_read and __interact_written. By
default it uses the preferred locale's encoding (such as those exported
using LC_* environment variables).

Trying to be backwards compatible with previous pexpect releases and
integrations, but not sure that it is yet, investigating the test
framework used here.

At the very least, by default, it should not dump the dreaded
UnicodeDecoderErrors that you would see previously.

XXX However input_filter and output_filter might be receiving unicode,
where previously they received str.
ignore log & .pyc in git repositories.