This reverts commit ecd1d020ab.
That commit caused test failures on my Debian Linux machine for all
changed test cases. We need to reconsider how that should get done.
Character set in POSIX is set by the locale defined (in decreasing order
of precedence) by the LC_ALL, LC_CTYPE and LANG environment variables (I
believe CHARSET is only historic). LC_ALL is cleared to ensure that
LC_CTYPE takes effect, but LC_ALL is not used to set the locale to
ensure that other parts of the locale aren't overriden, if set. Since
there doesn't seem to be a cross-platform way of specifying a UTF-8
locale, and not all systems may support UTF-8, a <precheck> is used
(where relevant) to skip the test if UTF-8 isn't in use. Test 1035 was
also converted to UTF-8 for consistency, as the actual character set
used there is irrelevant to the test.
