Fixed is_extent_var to ignore the first part of the split name components so as not to interfere with user vars named extent.
Fixed is_extent_var to ignore the first part of the split name components so as not to interfere with user vars named extent.


Former-commit-id: 8d7e43dc4bd06f61cda564df3ca5e69caa43587a
Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide