Adding upstream version 2.5.1.

Signed-off-by: Daniel Baumann <daniel@debian.org>

analysis/lang/en/plural_stemmer_test.go

@@ -0,0 +1,46 @@
+package en
+
+import "testing"
+
+func TestEnglishPluralStemmer(t *testing.T) {
+	data := []struct {
+		In, Out string
+	}{
+		{"dresses", "dress"},
+		{"dress", "dress"},
+		{"axes", "axe"},
+		{"ad", "ad"},
+		{"ads", "ad"},
+		{"gas", "ga"},
+		{"sass", "sass"},
+		{"berries", "berry"},
+		{"dresses", "dress"},
+		{"spies", "spy"},
+		{"shoes", "shoe"},
+		{"headaches", "headache"},
+		{"computer", "computer"},
+		{"dressing", "dressing"},
+		{"clothes", "clothe"},
+		{"DRESSES", "dress"},
+		{"frog", "frog"},
+		{"dress", "dress"},
+		{"runs", "run"},
+		{"pies", "pie"},
+		{"foxes", "fox"},
+		{"axes", "axe"},
+		{"foes", "fo"},
+		{"dishes", "dish"},
+		{"snitches", "snitch"},
+		{"cliches", "cliche"},
+		{"forests", "forest"},
+		{"yes", "ye"},
+	}
+
+	for _, datum := range data {
+		stemmed := stem(datum.In)
+
+		if stemmed != datum.Out {
+			t.Errorf("expected %v but got %v", datum.Out, stemmed)
+		}
+	}
+}