At this point, all remaining references to `MACINTOSH` are either part
of multi-value conditionals that `unifdef` was unable to determine the
final value for, or a `#define`, or a comment. I manually go through the
files with a Ctrl+Shift+F search (ignoring legacy/, to preserve useful
historic knowledge) and clean up each usage.
As part of that search, I discovered `lib/mac/` which I deleted wholly.
Test Plan:
On Mac, build both Debug and Release
```
cmake --build --preset mac --config Debug
cmake --build --preset mac --config Release
```
The MACINTOSH define refers to MacOS Classic (not OS X) which we do not
plan to support. Rather than carry the cruft forever, let's delete it.
NOTE: legacy/ is unused but we're keeping it around, so MACINTOSH uses
there are left alone.
Process used for this commit:
```
git rm -r mac
find . \( -iname "*.c" -or -iname "*.cpp" -or -iname "*.h" \) \
-exec unifdef -UMACINTOSH -o {} {} \;
git restore legacy
git add .
```
Test Plan:
On Mac, build both Debug and Release
```
cmake --build --preset mac --config Debug
cmake --build --preset mac --config Release
```
