Update pdp8_cpu.c

[poetnerd]

Rewrite of instruction decoder to implement Major States.

See issue 434, "Adding support for PDP- Major States within the CPU."
open-simh#434 (comment)

[markpizz]

Testing this on all existing compiler environments produces these problems:

1>..\PDP8\pdp8_cpu.c(412) : error C2143: syntax error : missing ';' before 'type'
1>..\PDP8\pdp8_cpu.c(484) : error C2065: 'op_code' : undeclared identifier
1>..\PDP8\pdp8_cpu.c(485) : error C2065: 'op_code' : undeclared identifier
1>..\PDP8\pdp8_cpu.c(526) : warning C4554: '&' : check operator precedence for possible error; use parentheses to clarify precedence

The first 3 are addressed by declaring "int op_code;" at the top of the routine.
The 4th is addressed by adding parenthesis where you want.

[poetnerd]

I've made the changes you suggest, and tested them on my Pi and my Mac.
See if that resolves the issues, and provokes no other issues.

[markpizz]

It looks clean now.

Before merging this into the master branch, I would suggest squashing the minor change into the reset of your changes as a single commit.

Meanwhile, I'm not sure how you created this as a pull request in your poetnerd/simh repo. To get it merged upstream, you will need to create a pull request in github.com/open-simh/simh

[poetnerd]

Thanks for the help, Mark. Although I'm an old hand at C coding, I'm a noob when it comes to using github. I've squashed the commits here, and made an upstream pull request now. open-simh#472