This is where "ports" of apreq-2 are made.

To port apreq-2 to a particular application, you need
to provide definitions for all the declarations in 
src/apreq_env.h.

Layout:

        env/
            Makefile.am  - build system configuration
            *.c          - available environments
            c-modules/   - test modules
            t/*.t        - unit tests

