32-bit version discontinued

It's time to streamline development by dropping support for the 32-bit version of Diesel Railcar Simulator and focus on the 64-bit version only:

• Steam hardware report shows that nobody is using the 32-bit version of DRS anymore (of those players that share their hardware specs with Steam)
• 64-bit consumer CPUs were introduced some 20 years ago, so they should be commonplace
• The 32-bit version has serious performance problems owing to the max 4GB of usable RAM limit for 32-bit programs, requiring constant paging to hard drive because the game often needs more than 4GB RAM
• Some people get confused and try to use the 32-bit version even on a 64-bit system, leading to poor performance and crashes for no good reason
• Dropping 32-bit support makes development easier and faster

In future versions there will still be two exe files (one with the "64-bit" suffix and one without), but the files will otherwise be identical 64-bit executables.