py: Compress load-int, load-fast, store-fast, unop, binop bytecodes.
There is a lot potential in compress bytecodes and make more use of the coding space. This patch introduces "multi" bytecodes which have their argument included in the bytecode (by addition). UNARY_OP and BINARY_OP now no longer take a 1 byte argument for the opcode. Rather, the opcode is included in the first byte itself. LOAD_FAST_[0,1,2] and STORE_FAST_[0,1,2] are removed in favour of their multi versions, which can take an argument between 0 and 15 inclusive. The majority of LOAD_FAST/STORE_FAST codes fit in this range and so this saves a byte for each of these. LOAD_CONST_SMALL_INT_MULTI is used to load small ints between -16 and 47 inclusive. Such ints are quite common and now only need 1 byte to store, and now have much faster decoding. In all this patch saves about 2% RAM for typically bytecode (1.8% on 64-bit test, 2.5% on pyboard test). It also reduces the binary size (because bytecodes are simplified) and doesn't harm performance.