gdb command updates

[nobodynate]

Thank you for posting this course. It's been immensely helpful as I use gdb for the first time!

I ran into a few errors while going through the x86 course, though the issues seem to be realted to changes in gdb so probably applicable to other sections.

Printing variables:
The course uses print constant but I had to use print (int) constant to avoid an unknown type error.

Setting variables:
The course uses set constant = 666 but I had to use set $constant = (int) 666 to avoid an unknown type error.

This was on GNU gdb (Debian 13.1-2) 13.1