Unnecessary sign extend in fetch_operand()

[rkrten]

Hi, I believe that the M6809::fetch_operand() should have the extend8() around the immediate case fetch() removed.

This manifests as causing the disassembler to display LDA #$F9 as LDA#$FFF9; that is, a gratuitous sign extension.

The extend8() doesn't appear to be required for the 6809 emulation; I've removed it on my system and everything still runs fine.

[raybellis]

Yes, you appear to be correct - thanks! Resolved in 89584d0.