Add support for multiple controllers and device types. Make Genode to
Libretro input mapping configurable, which relieves the need to
externally remap Genode keycodes to conform to static Libretro mapping.
Send keyboard input to a optional keyboard callback set by the core to
complete keyboard support.
Ref #89
This patch introduces a single-file XML editor driven by Report clients.
The xml_editor component manages edits to a file and the xml_term_edit
component is a terminal-based frontend.
Fix#75
