Fix compile error with GCC 15 (-std=c23)

[ueno]

When compiling on Fedora rawhide, it fails with:

In file included from ../internal/api/atomic_bool.h:23,
                 from ../internal/api/mutex_w.h:24,
                 from ../drng/src/seeded_rng.c:28:
../internal/api/bool.h:31:8: error: cannot use keyword ‘false’ as enumeration constant
   31 | enum { false, true };
      |        ^~~~~
../internal/api/bool.h:31:8: note: ‘false’ is a keyword with ‘-std=c23’ onwards
../internal/api/bool.h:32:15: error: ‘bool’ cannot be defined via ‘typedef’
   32 | typedef _Bool bool;
      |               ^~~~
../internal/api/bool.h:32:15: note: ‘bool’ is a keyword with ‘-std=c23’ onwards
../internal/api/bool.h:32:1: warning: useless type name in empty declaration
   32 | typedef _Bool bool;
      | ^~~~~~~

The first commit should fix it, though the second commit is just a cosmetics.

[smuellerDD]

Applied, thanks