Read uint to int

Addresses tinylib#134 in a way that makes
it more interoperable with other msgpack libraries.

The actual code borrowed from librato#1

Author: antoniomo

msgp/read.go

@@ -607,6 +607,42 @@ func (m *Reader) ReadInt64() (i int64, err error) {
 		i = getMint64(p)
 		return
 
+	case muint8:
+		p, err = m.R.Next(2)
+		if err != nil {
+			return
+		}
+		i = int64(getMuint8(p))
+		return
+
+	case muint16:
+		p, err = m.R.Next(3)
+		if err != nil {
+			return
+		}
+		i = int64(getMuint16(p))
+		return
+
+	case muint32:
+		p, err = m.R.Next(5)
+		if err != nil {
+			return
+		}
+		i = int64(getMuint32(p))
+		return
+
+	case muint64:
+		p, err = m.R.Next(9)
+		if err != nil {
+			return
+		}
+		u := getMuint64(p)
+		if u > math.MaxInt64 {
+			err = badPrefix(IntType, lead)
+		}
+		i = int64(u)
+		return
+
 	default:
 		err = badPrefix(IntType, lead)
 		return

msgp/read_bytes.go

@@ -395,6 +395,46 @@ func ReadInt64Bytes(b []byte) (i int64, o []byte, err error) {
 		o = b[9:]
 		return
 
+	case muint8:
+		if l < 2 {
+			err = ErrShortBytes
+			return
+		}
+		i = int64(getMuint8(b))
+		o = b[2:]
+		return
+
+	case muint16:
+		if l < 3 {
+			err = ErrShortBytes
+			return
+		}
+		i = int64(getMuint16(b))
+		o = b[3:]
+		return
+
+	case muint32:
+		if l < 5 {
+			err = ErrShortBytes
+			return
+		}
+		i = int64(getMuint32(b))
+		o = b[5:]
+		return
+
+	case muint64:
+		if l < 9 {
+			err = ErrShortBytes
+			return
+		}
+		u := getMuint64(b)
+		if u > math.MaxInt64 {
+			err = badPrefix(IntType, lead)
+		}
+		i = int64(u)
+		o = b[9:]
+		return
+
 	default:
 		err = badPrefix(IntType, lead)
 		return