Add reference file for XXHash32 using a small number of bytes.

This hits the edge cases for completing the hash with leftover bytes and
no processing in the main update method.

Author: aherbert

src/test/java/org/apache/commons/codec/digest/XXHash32Test.java

@@ -61,8 +61,10 @@ public XXHash32Test(final String path, final String c) throws IOException {
     public static Collection<Object[]> factory() {
         return Arrays.asList(new Object[][] {
             // reference checksums created with xxh32sum
+            // http://cyan4973.github.io/xxHash/
             { "bla.tar", "fbb5c8d1" },
             { "bla.tar.xz", "4106a208" },
+            { "small.bin", "f66c26f8" },
         });
     }
 

src/test/resources/small.bin

@@ -0,0 +1 @@
+��4e�cǗJ�