Add special consideration for rlcompleter. As a side effect of

Add special consideration for rlcompleter.  As a side effect of
initializing GNU readline, setlocale(LC_CTYPE, "") is called, which
changes the <ctype.h> macros to use the "default" locale (which isn't
the *initial* locale -- the initial locale is the "C" locale in which
only ASCII characters are printable).  When the default locale is e.g.
Latin-1, the repr() of string objects can include 8-bit characters
with the high bit set; I believe this is due to the recent
PRINT_MULTIBYTE_STRING changes to stringobject.c.  This in turn screws
up test_pyexpat and test_rotor, which depend on the repr() of 8-bit
strings with high bit characters.

The solution (for now) is to force the LC_CTYPE locale to "C" after
importing rlcompleter.  This is the locale required by the test suite
anyway.