The X11 option.

This plugin creates an (x11) package.  It is built in the GNU standard
way (below).  It expects the pkg-config command to know about x11, and
for certain auxiliary headers to be available.  On Ubuntu this means
the pkg-config, libx11-dev and x11proto-dev packages must be installed
before running the configure script.

The GNU standard way:

    ./configure ...
    make all
    make check
    make install

The last command will attempt to create a subdirectory in the first
directory on Scheme's library path.  If that directory is not writable
by you, super-user privileges may be required.

You can put a writable directory at the front of your Scheme's library
path by setting the MITSCHEME_LIBRARY_PATH environment variable and
creating a short optiondb file.

    mkdir ~/.mit-scheme-x86-64
    echo "(further-load-options #t)" > ~/.mit-scheme-x86-64/optiondb.scm
    export MITSCHEME_LIBRARY_PATH=\
        ~/.mit-scheme-x86-64:/usr/local/lib/mit-scheme-x86-64
    make install

To use:

    (load-option 'x11)
    (define dev (make-graphics-device 'x))

To import into a CREF package set, add this to your .pkg file:

    (global-definitions x11/)

    (define-package (your package name)
      (parent (your package parent))
      (import (x11)
              xterm-open-window
              ...))
