Reindent all C sources to the canonical stroustrup style

Mechanical whitespace-only change across src/, include/, tests/, and
util/, applied with scripts/reindent.sh. No behavioral change.

Most files already conformed. The genuine outliers indented at 2 columns
(json_helpers.c, util.c from akgl_rectangle_points onward, assets.c,
staticstring.c, akgl_actor_add_child, util.h, staticstring.h) or used
spaces where the canonical form is a tab (draw.c). cc-mode also re-aligns
line-continuation backslashes in multi-line macros to its default
c-backslash-column, which is required for the tree to be a fixed point of
the indenter.

Verified whitespace-only: `git diff -w` over this change is empty apart
from three trailing blank lines removed at EOF in src/heap.c,
src/registry.c, and tests/tilemap.c. The build produces no new errors and
ctest is unchanged at 13/14, with `character` still the one intentional
failure.

The tree is now a fixed point of `scripts/reindent.sh --check`.

include/akgl/SDL_GameControllerDB.h is generated and excluded.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Co-Authored-By: Andrew Kesterson <andrew@aklabs.net>

src/heap.c

@@ -146,7 +146,7 @@ akerr_ErrorContext *akgl_heap_release_character(akgl_Character *basechar)
     akgl_Iterator opflags;
     FAIL_ZERO_RETURN(errctx, basechar, AKERR_NULLPOINTER, "NULL character reference");
     AKGL_BITMASK_CLEAR(opflags.flags);
-  
+
     if ( basechar->refcount > 0 ) {
 	basechar->refcount -= 1;
     }
@@ -201,4 +201,3 @@ akerr_ErrorContext *akgl_heap_release_string(akgl_String *ptr)
     }
     SUCCEED_RETURN(errctx);
 }
-