All of the include files in the win32/gnu/ subdirectory were generated
using the standard build system on a system with both MSYS2 and TDM-GCC
installed.  Normally you'd think that this would be the way to go (hey,
just use the regular old buildtools!), and normally you'd be right... But
in this case we don't want to have dependencies on DLLs distributed only
with MSYS, and there are other things keeping regular old buildtools from
working.

The TDM-GCC-specific Makefile is pretty simple (except for the pattern rules
that enable building all the binaries) and was constructed by observing
the output of make from the MSYS2 build.

Other than the GNUlib stuff, the Windows emulation of dirent (dirent.[ch])
was taken from the GNU make 3.82 distribution.  dirent.h was modified
slightly because it assumed that MinGW ==> MSYS, which is not true.

- Cloyce D. Spradling, 2 Dec 2015
