sequentially usage of bits8 during encoding produce incorrect flat.

[rssh]

Next test illustrate this:

test("encode/decode numeric analog of SIRType Fun[Int,Fun[Int,Int]]") {
        val enc = new EncoderState(20)
        enc.bits(4,8)
        enc.bits(4,1)
        enc.bits(4,8)
        enc.bits(4,1)
        enc.bits(4,1)
        val decoder = new DecoderState(enc.buffer)
        val t1 = decoder.bits8(4)
        assert(t1 == 8)
        val t2 = decoder.bits8(4)
        assert(t2 == 1)
        val t3 = decoder.bits8(4)
        assert(t3 == 8)
        val t4 = decoder.bits8(4)
        assert(t4 == 1)
        val t5 = decoder.bits8(4)
        assert(t5 == 1)
    }