Fixes #900 pop-in animation being affected by framerate

Fixes #906

Uses the old displacement of the minecart to position the mark relative
to its destination. It's not completely correct, but it works.

Fixes #916

This reverts merge request !1920

This prevents axis events from trickling out of the menu and taking
effect in G_Responder when they aren't hitting the digital deadzone
needed to be mapped into internal menu key events.

Was erroneously mapping events inside the deadzone as key down and vice
versa.

Also fixed issues with the d_netcmd.c file/folder adding logic.