cpu.x86: Fix the popcnt? word alien-assembly. XOR the return-reg RAX before calling BT/BSET because XOR clears the CF and the whole thing becomes a no-op. Change popcnt instruction to opt-out rather than opt-in. Fixes #663.
cpu.x86: Fix the popcnt? word alien-assembly. XOR the return-reg RAX before calling BT/BSET because XOR clears the CF and the whole thing becomes a no-op. Change popcnt instruction to opt-out rather than opt-in. Fixes #663.

mcandre/factor,mcandre/factor,mcandre/factor,mcandre/factor,mcandre/factor,mcandre/factor,mcandre/factor