[mapplauncherd] Remove splash support.

This feature only encourages poor application interactivity: anything which is
sufficiently slow to require a splash screen should be made faster instead.

In addition to that, the feature is poorly implemented (X11-specific), and thus
useless. Rip it out, and remove the last dependency on X11 from applauncherd.
Merge pull request #7 from rburchell/splash

[mapplauncherd] Remove splash support.