char-set:ascii is the only char-set consisting of a single contiguous
range, and there was an off-by-one error for that case.
* libguile/unidata_to_charset.pl (compute): fix off-by-one
* test-suite/lib.scm (with-locale, with-locale*): new test functions
* test-suite/tests/encoding-escapes: don't fail if en_US.utf8 doesn't exist
* test-suite/tests/encoding-iso88591.test: set and restore locale, if
possible
* test-suite/tests/encoding-iso88597.test: set and restore locale, if
possible
* test-suite/tests/encoding-utf8.test: set and restore locale, if possible
* test-suite/tests/srfi-14.test: don't need to setlocale to Latin-1 to
test Latin-1 since string conversion is handled at read/compile time.
Set and restore locale, if possible.