xemu issues

[Tatsh]

• [x] Version does not display (just shows "v" in window title) place to patch
• [x] .desktop entry
  • [x] Fix name, icon, remove NoDisplay
• [x] Install the debug binary if split-debug is enabled
• [x] Fix install so that the output binary is named xemu, allowing src_install() to be default
• [x] Minimalise patch for bin name
• [x] Skip tests if ! use test
• [x] Correct icon