Update comments to indicate the ExternalCode API is not fully supported by the implementation.
Update comments to indicate the ExternalCode API is not fully
supported by the implementation.


Former-commit-id: f3a9b514c83f6effb9a7387e7772721018eaf3a1
Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide