wildmatch test: cover a blind spot in "/" matching

A negated character class that does not include '/', e.g. [^a-z]:

 - Should match '/' when doing "wildmatch"
 - Should not match '/' when doing "pathmatch"

Add two tests to cover these cases.

Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t3070-wildmatch.sh

@@ -82,6 +82,7 @@ match 1 0 'foo/bar' 'foo/**/bar'
 match 1 0 'foo/bar' 'foo/**/**/bar'
 match 0 0 'foo/bar' 'foo?bar'
 match 0 0 'foo/bar' 'foo[/]bar'
+match 0 0 'foo/bar' 'foo[^a-z]bar'
 match 0 0 'foo/bar' 'f[^eiu][^eiu][^eiu][^eiu][^eiu]r'
 match 1 1 'foo-bar' 'f[^eiu][^eiu][^eiu][^eiu][^eiu]r'
 match 1 0 'foo' '**/foo'
@@ -225,6 +226,7 @@ pathmatch 0 foo/bba/arr 'foo/*z'
 pathmatch 0 foo/bba/arr 'foo/**z'
 pathmatch 1 foo/bar 'foo?bar'
 pathmatch 1 foo/bar 'foo[/]bar'
+pathmatch 1 foo/bar 'foo[^a-z]bar'
 pathmatch 0 foo '*/*/*'
 pathmatch 0 foo/bar '*/*/*'
 pathmatch 1 foo/bba/arr '*/*/*'