To build the optional InChI support, run cmake with the
-DRDK_BUILD_INCHI_SUPPORT=ON argument. If InChI sources could not be
found, the CMake build system will attempt to download the InChI
distribution from the following URL:

http://www.inchi-trust.org/wp/wp-content/uploads/2014/06/INCHI-1-API.zip

The default download URL and MD5 checksum can be overridden with the
following CMake definitions:

INCHI_URL
INCHI_MD5SUM

If INCHI_URL is set to "", no download will be attempted.
If INCHI_MD5SUM is set to "", no MD5 checksum will be performed.

If you prefer to install InChI sources manually, please follow these
instructions:

1. Download the zip file from
   http://www.inchi-trust.org/wp/wp-content/uploads/2014/06/INCHI-1-API.zip

2. Unzip the package, which creates a INCHI-1-API folder.

3. In the unzipped folder, find INCHI-1-API/INCHI_API/inchi_dll, under which
   there are 73 files including things like ichi.h and ikey_dll.c. Create a
   'src' directory inside the same directory that contains this README file
   you are readingCopy, and copy all those 73 files 'src' you have just
   created. The actual path is '$RDBASE/External/INCHI-API/src'.

4. Rerun `cmake` with `-DRDK_BUILD_INCHI_SUPPORT=ON` as an additional argument

Alternatively, if you are on a UNIX variant system (Linux, Mac OS X, Cygwin,
etc), you may invoke the included script `download-inchi.sh`:
	
	$ bash download-inchi.sh

When the download is successful, rerun`cmake` with
`-DRDK_BUILD_INCHI_SUPPORT=ON` as an additional argument