(svn r8841) -Fix

Remove {,u}intswap() and replace them by Swap()

(svn r8767) -Fix

-Codechange: Do not hardcode the catchment radius of airports, but hold the information in AirportFTAClass
-Fix (r979): The default AI tested possible airport locations with a fixed catchment radius instead of the radius of the to be built airport

(svn r8755) -Fix

Abbreviate GetAirport(st->airport_type) to st->Airport()

(svn r8747) -Fix

-Codechange: Make the encoding of accepted aircraft types of airports a bit more sensible and move the enum into struct AirportFTAClass

(svn r8660) -Fix

-Codechange: Remove _avail_aircraft
Its name is misleading. It is rather _avail_airports, but then only some of them, which leads to inconsistencies when using it.
Further it is unnecessary to store it in savegams.

(svn r8455) -Codechange: Give a more meaningful name (railveh_type)to member flags of RailVehInfo, as well as changing the code to reflect the fact that it was not a flag but rather a one value only variable. Doing so, some evaluations have been simplified.
-Codechange: Add and use RAILVEH_SINGLEHEAD when railveh_type is set to 0, which was implicit before.
-Cleanup: Remove some extraneous parenthesis.

(svn r8385) -Fix

-Regression (r8314): I only did half the necessary changes to move railtype from Engine to RailVehicleInfo. Now do the rest.

(svn r8276) -Fix

Change the signature of Swap() to be less error prone, i.e. pass the variables to be swapped by reference instead of passing pointers to the variables.
Just do Swap(x, y) instead of Swap(&x, &y). This prevents accidents when the variables are pointers.