v1.0.5 hashing improvements and fix

• fix hashing on ARM CPUs
• optimize hashing by using specialized xxhash implementations
• reduce variable allocations in get functions
• removed obsolete 0 length checks

It is noticeable faster than the current version of HaxMap is able to handle collisions of valid 0 hash values:

BenchmarkReadHashMapUint-8                	 1314156	       955.6 ns/op
BenchmarkReadHaxMapUint-8                 	  872134	      1316 ns/op (can not handle hash 0 collisions)

// works for this library, fails for HaxMap
func TestHash0Collision(t *testing.T) {
	m := New[string, int]()
	staticHasher := func(key string) uintptr {
		return 0
	}
	m.SetHasher(staticHasher)
	m.Set("1", 1)
	m.Set("2", 2)
	_, ok := m.Get("1")
	if !ok {
		t.Error("1 not found")
	}
	_, ok = m.Get("2")
	if !ok {
		t.Error("2 not found")
	}
}