Fix wildcard expansion in directories without read permissions

When performing wildcard expansion with a literal path segment,
instead of enumerating the files in the directory, simply apply the
path segment as if we found the directory and continue on. This
enables us to expand strings that contain unreadable directory
components (common with $HOME) and also improves performance, since
we don't waste time enumerating directories unnecessarily. Adds
a test too.

Fixes #2099

tests/test5.in

@@ -23,3 +23,15 @@ switch $smurf
 	case "?????"
 		echo Test 3 pass
 end
+
+# Verify that we can do wildcard expansion when we
+# don't have read access to some path components
+# See #2099
+set -l where /tmp/fish_wildcard_permissions_test/noaccess/yesaccess
+mkdir -p $where
+chmod 300 (dirname $where) # no read permissions
+mkdir -p $where
+touch $where/alpha.txt $where/beta.txt $where/delta.txt
+echo $where/*
+chmod 700 (dirname $where) # so we can delete it
+rm -rf /tmp/fish_wildcard_permissions_test

tests/test5.out

@@ -1,3 +1,4 @@
 Test 1 pass
 Test 2 pass
 Test 3 pass
+/tmp/fish_wildcard_permissions_test/noaccess/yesaccess/alpha.txt /tmp/fish_wildcard_permissions_test/noaccess/yesaccess/beta.txt /tmp/fish_wildcard_permissions_test/noaccess/yesaccess/delta.txt