Fix 6502 instruction set

[vxgmichel]

I've noticed two errors in the 6502 instruction set:

• asl zpg_addr => 0x06: http://6502.org/tutorials/6502opcodes.html#ASL
• bcs rel_addr => 0xB0: http://6502.org/tutorials/6502opcodes.html#BCS

For the record, I have not checked all the op codes systematically so there might be more errors.

[hlorenzi]

Really, really nice catch!

[vxgmichel]

Thankfully I've been testing my programs on an emulator before running them on actual hardware so I've been able to figure it out quite quickly :)