Add 32-bit support

[tshino]

Thanks to issue #2 and the nice reporter, now it is clear that to build 32-bit softcam.dll is required to support 32-bit camera applications.

• Adding 32-bit configurations to all projects and solutions is a relatively easy task.
• Study/investigating and design are required for the following issues:
  • Naming of DLL and LIB. Good practice? Adding '32' suffix?
  • dist directory layout.
  • Installing process. Require running the installer once for each mode?
  • Class ID/name. Should they be different?
  • Use cases with a mix of 32-bit and 64-bit for the DLL and app. Is it possible? Does it work properly?

[tshino]

Done!

Decisions/Lessons learned are as follows:

• DLL names: Should be consistent. No need to add the suffix 32.
• dist directory layout: Separate directories for each platform (x64, Win32) are reasonable.
• Installing process: Needs to run once for each mode.
• Class ID/name: Should be consistent.
• Mixture use case: Possible. In our architecture, the DLLs at apps on each side communicate through shared memory, which can be accessible for both 32-bit and 64-bit DLLs at the same time.
• Calling conventions matter in 32-bit mode. Explicit declarations were needed at some points in the code.