It includes a fallback list of fourccs. Otherwise we might miss some
DRM_FORMAT definition.
This happens in SLES12:
```
../testsuite/gdk/dmabufformats.c: In function ‘test_dmabuf_formats_basic’:
../testsuite/gdk/dmabufformats.c:29:56: error: ‘DRM_FORMAT_ABGR16161616F’ undeclared (first use in this function); did you mean ‘DRM_FORMAT_ABGR2101010’?
29 | g_assert_true (gdk_dmabuf_formats_contains (formats, DRM_FORMAT_ABGR16161616F, DRM_FORMAT_MOD_LINEAR));
```
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