aware-tectonic-engine-xdvipdfmx

The `xdvipdfmx` program as a reusable crate. This is the Aware Software fork of tectonic_engine_xdvipdfmx 0.4.4: identical to upstream except that the embedded xdvipdfmx exposes a configurable PDF page-origin offset (defaulting to upstream's 1 inch) so callers can request a 0-inch origin.