Make opcode disasm names match reference impl.

This commit modifies the names of opcdoes shown in the oneline script
disassembly to match the reference implementation.  In particular
OP_1NEGATE, and OP_0 through OP_16 are changed to the raw numbers
they represent when doing oneline disassembly.  When doing full
disassembly, the full opcode names are still shown.

ok @owainga.