Fix LOCK 16-bit INC/DEC using 32-bit primop in interpreter path (#1070)

RunF066 handles F0 66 FF /0,/1 (LOCK INC/DEC Ew). The non-DYNAREC path applied inc32/dec32 to ED->dword[0], corrupting the upper 16 bits and computing OF/SF/ZF/AF/PF at the wrong operand width. The DYNAREC path just above correctly uses inc16/dec16, as does the non-LOCK Grp5 Ew handler in x86run66.c (EW->word[0] = inc16/dec16). Narrow the interpreter LOCK path to ED->word[0] with inc16/dec16.