[MAT-450] Update NativeLibraryLoader for 32-bit

The GCC runtime libraries have different names and a different
default location on 32-bit Windows. This commit accommodates this
by:

- Adding a new platform, called 'w32' for 32-bit Windows.
- Modifying syslibs.py to copy the correct libraries from the
  correct location depending on the architecture. The target
  architecture is determined by calling gcc -dumpmachine.
- Modifying the NativeLibraries.properties file to differentiate
  between 32- and 64-bit systems and adding a set of library
  entries for 32-bit Windows.
- Modifying the NativeLibraries class so that it doesn't abort on
  32-bit Windows.
- Modifying the set_platform_folder macro to use the "w32" folder
  when building for 32-bit Windows
- Use the set_platform_folder macro in the root CMakeLists.txt -
  this required some movement of includes, and is a little fiddly
  because of inconsistencies between the platform code used by the
  jar and the platform code used by the build system - e.g.
  mac/osx and lin/lnx.
- Update the blob combiner to combine libraries from the w32
  platform.