internal/d3d11: extract Direct3D API to separate package

We're about the merge the Direct3D backend into package gpu. Extract the
raw Direct3D API to its own package, just like package glimpl.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

app/loop.go

@@ -10,6 +10,8 @@ import (
 	"gioui.org/app/internal/window"
 	"gioui.org/gpu"
 	"gioui.org/op"
+
+	_ "gioui.org/app/internal/d3d11"
 )
 
 type renderLoop struct {