add pc104alt rule
The original commit for pc104alt did not include a rule to access it. The first patch does that, and adds a missing rule for pc86 as well.
The two follow up patches address some issues that I noticed while adding pc104alt. Patch 2 removes the unreachable pc(latitude). Patch 3 removes some dead code in geometry/pc that has been unreachable for eleven years.
Edited by Peter Hutterer