This updates `fmt` to the latest version and moves to just being a copy
of their repo to make updating easier (no editing their cmake / figuring
out which files to minimally include).
The motivation for this is now that we switched to C++ 20, there were a
ton of deprecated function usages that is going away in future compiler
versions. This gets rid of all those warnings.
* [goalc] macro expansion in integer constants
* working
* didn't break it yet
* support conditional compilation
* fix up some more small bugs
* fix duplicate evaluation of bitfield definitions
* paranoid
Tyler Wilding
ManDude
water111