hash.fnv1a: add fnv1a.sum64_bytes and fnv1a.sum32_bytes, add doc comments and tests

vlib/hash/fnv1a/fnv1a_test.v

@@ -1,12 +1,29 @@
 import hash.fnv1a
 
-fn test_fnv1a() {
+fn test_fnv1a_sum32() {
+	$if windows {
+		return
+	}
+	ahash := '10bc2abf'
+	a := 'apple'
+	b := fnv1a.sum32_string(a)
+	c := fnv1a.sum32(a.bytes())
+	d := unsafe { fnv1a.sum32_bytes(a.str, a.len) }
+	assert b.hex() == ahash
+	assert c.hex() == ahash
+	assert d.hex() == ahash
+}
+
+fn test_fnv1a_sum64() {
 	$if windows {
 		return
 	}
 	a := 'apple'
+	ahash := 'f74a62a458befdbf'
 	b := fnv1a.sum64_string(a)
 	c := fnv1a.sum64(a.bytes())
-	assert b.hex() == 'f74a62a458befdbf'
-	assert c.hex() == 'f74a62a458befdbf'
+	d := unsafe { fnv1a.sum64_bytes(a.str, a.len) }
+	assert b.hex() == ahash
+	assert c.hex() == ahash
+	assert d.hex() == ahash
 }