Proposed BC Changes

Based on recent discussions, here's some changes I'm thinking of making
to the bytecode format in release 1.5 (version 5 bytecode). These are
all mostly trivial. Just wanted to run this by everyone in case I
misunderstood something or there are issues I haven't foreseen.

case 4: // 1.3.1 (Not Released)
    // In version 4, basic blocks have a minimum index of 0 whereas all the
    // other primitives have a minimum index of 1 (because 0 is the "null"
    // value. In version 5, we made this consistent.
    hasInconsistentBBSlotNums = true;
    // In version 4, the types SByte and UByte were encoded as vbr_uint so that
    // signed values > 63 and unsigned values >127 would be encoded as two
    // bytes. In version 5, they are encoded directly in a single byte.
    hasVBRByteTypes = true;
    // In version 4, modules begin with a "Module Block" which encodes a 4-byte
    // integer value 0x01 to identify the module block. This is unnecessary and
    // removed in version 5.
    hasUnnecessaryModuleBlockId = true;


erk, I meant to say "in release 1.4 (version 5 bytecode)"