The 'visual_studio' subdirectory provides some Cygwin Bash shell script
fragments that can be used to provide Visual Studio environment variables
and Visual Studio executables to the Cygwin Bash environment.  This is to
support the use of Cygwin's Gnu Make in building Visual C++ versions of MX.

Each version of Visual Studio needs its own different version of the
shell script fragment.  Usually, the process consists of identifying
which shell script fragment applies to the Visual Studio version you
have and then modifying the PROGRAM_FILES_DIR variable to match the
location that you have installed Visual Studio to.  Typically, this has
already been set in the script to either "C:\\Program Files (x86)" or
"C:\\Program Files" depending on whether you are running a 64-bit or
a 32-bit version of Windows.