Blender Git Commit Log

Attempt to fix build error on MSVC and warnings on some other compilers

On MSVC it failed with this error:
```
sourceblenderblenkernelBKE_context.h(361,20): error C2526:
'CTX_wm_asset_handle': C linkage function cannot return C++ class 'AssetHandle'
```

On Apple Clang I would get this:
```
warning: 'CTX_wm_asset_handle' has C-linkage specified, but returns incomplete
type 'struct AssetHandle' which could be incompatible with C
[-Wreturn-type-c-linkage]
struct AssetHandle CTX_wm_asset_handle(const bContext *C, bool *r_is_valid);
^
1 warning generated.
```

Just include the asset header defining the type for now, it should later on be
solved properly with a better design for `AssetHandle`.