Do not marshall bits in little-endian encoding

[dr-orlovsky]

Little-endian encoding used in bit marshaling leads to situations where lately encoded arguments go before first ones.

Assume we have an instruction Instr { arg1: u4, arg2: u4 }, where arg1 = 0b_0110; arg2 = 0b_1001. These arguments will be marshaled as 0b_10010110 byte, which is quite contrary to intuition of 0b_01101001.

A negative side-effect of this is the fact when multiple instructions share the same op-code byte and use several bits to further clarify the instruction, these bits are marshaled after argument bits.